Until now we were only GC'ing RCE entries, but OCE entries (top-level
cache entry for an OID) were never GC'ed thus allowing cache size to
grow infinitely.

Even though the average N(allocations) stays the same this change lowers
pressure on amount of memory allocated and thus helping avoid some GC
speeds things up (see attachment).

Notes:

1. Hit*/size=0 increase is probably due to Cache.entryMap going to
   empty/1-element back and forth constantly. size/0 is not going to
   happen in practice and so this wat we can accept regression here.

   ( still NoHit*/size=0 works faster ).

2. HitProc/size=* "regression should be within noise"

name                        old time/op    new time/op    delta
NoopStorage-4                 56.6ns ± 1%    56.2ns ± 0%       ~     (p=0.079 n=5+5)
CacheStartup-4                1.24µs ± 6%    1.28µs ± 9%       ~     (p=0.595 n=5+5)
CacheNoHit/size=0-4           1.44µs ± 4%    0.93µs ± 2%    -35.26%  (p=0.008 n=5+5)
CacheNoHit/size=16-4          1.43µs ± 5%    0.92µs ± 1%    -35.19%  (p=0.008 n=5+5)
CacheNoHit/size=128-4         1.45µs ± 3%    0.94µs ± 1%    -35.03%  (p=0.008 n=5+5)
CacheNoHit/size=512-4         1.44µs ± 4%    0.97µs ± 2%    -32.64%  (p=0.008 n=5+5)
CacheNoHit/size=4096-4        1.45µs ± 2%    1.07µs ± 0%    -25.85%  (p=0.008 n=5+5)
CacheHit/size=0-4              131ns ± 2%     276ns ±22%   +110.99%  (p=0.008 n=5+5)
CacheHit/size=16-4             122ns ± 1%     121ns ± 1%       ~     (p=0.079 n=5+5)
CacheHit/size=128-4            126ns ± 2%     125ns ± 1%       ~     (p=0.563 n=5+5)
CacheHit/size=512-4            127ns ± 1%     126ns ± 0%       ~     (p=0.095 n=5+4)
CacheHit/size=4096-4           128ns ± 0%     128ns ± 0%       ~     (p=0.556 n=5+4)
NoopStoragePar-4              30.6ns ± 4%    31.2ns ±10%       ~     (p=0.690 n=5+5)
CacheStartupPar-4             1.44µs ± 5%    1.43µs ± 3%       ~     (p=0.690 n=5+5)
CacheNoHitPar/size=0-4        1.62µs ± 4%    1.04µs ± 1%    -35.76%  (p=0.008 n=5+5)
CacheNoHitPar/size=16-4       1.65µs ± 4%    1.05µs ± 1%    -36.39%  (p=0.008 n=5+5)
CacheNoHitPar/size=128-4      1.64µs ± 5%    1.05µs ± 1%    -35.84%  (p=0.008 n=5+5)
CacheNoHitPar/size=512-4      1.62µs ± 3%    1.08µs ± 1%    -33.10%  (p=0.008 n=5+5)
CacheNoHitPar/size=4096-4     1.68µs ± 1%    1.18µs ± 0%    -29.44%  (p=0.008 n=5+5)
CacheHitPar/size=0-4           215ns ± 0%     383ns ± 2%    +78.23%  (p=0.008 n=5+5)
CacheHitPar/size=16-4          214ns ± 2%     214ns ± 0%       ~     (p=0.786 n=5+5)
CacheHitPar/size=128-4         210ns ± 0%     209ns ± 0%       ~     (p=0.079 n=5+5)
CacheHitPar/size=512-4         207ns ± 0%     206ns ± 0%     -0.48%  (p=0.008 n=5+5)
CacheHitPar/size=4096-4        204ns ± 0%     202ns ± 0%     -0.98%  (p=0.000 n=5+4)
NoopStorageProc-4             31.4ns ± 7%    33.7ns ± 5%       ~     (p=0.151 n=5+5)
CacheStartupProc-4            1.13µs ± 5%    1.12µs ± 3%       ~     (p=0.690 n=5+5)
CacheNoHitProc/size=0-4       1.12µs ± 5%    0.62µs ± 1%    -44.52%  (p=0.008 n=5+5)
CacheNoHitProc/size=16-4      1.14µs ± 6%    0.63µs ± 1%    -45.14%  (p=0.008 n=5+5)
CacheNoHitProc/size=128-4     1.06µs ± 5%    0.64µs ± 2%    -40.12%  (p=0.008 n=5+5)
CacheNoHitProc/size=512-4     1.14µs ±11%    0.69µs ± 4%    -39.87%  (p=0.008 n=5+5)
CacheNoHitProc/size=4096-4    1.14µs ± 9%    0.68µs ± 2%    -40.21%  (p=0.008 n=5+5)
CacheHitProc/size=0-4         56.5ns ± 7%    84.6ns ±14%    +49.66%  (p=0.008 n=5+5)
CacheHitProc/size=16-4        55.8ns ± 0%    62.0ns ± 6%    +11.03%  (p=0.008 n=5+5)
CacheHitProc/size=128-4       56.6ns ± 0%    60.9ns ± 4%     +7.63%  (p=0.008 n=5+5)
CacheHitProc/size=512-4       57.3ns ± 0%    64.1ns ± 7%    +11.83%  (p=0.016 n=4+5)
CacheHitProc/size=4096-4      61.6ns ± 1%    69.7ns ± 5%    +13.29%  (p=0.008 n=5+5)

name                        old alloc/op   new alloc/op   delta
NoopStorage-4                  0.00B          0.00B            ~     (all equal)
CacheStartup-4                  269B ± 0%      285B ± 0%     +5.95%  (p=0.008 n=5+5)
CacheNoHit/size=0-4             225B ± 0%      153B ± 0%    -32.12%  (p=0.008 n=5+5)
CacheNoHit/size=16-4            225B ± 0%      153B ± 0%    -32.00%  (p=0.029 n=4+4)
CacheNoHit/size=128-4           225B ± 1%      153B ± 0%    -31.76%  (p=0.008 n=5+5)
CacheNoHit/size=512-4           225B ± 1%      154B ± 0%    -31.50%  (p=0.008 n=5+5)
CacheNoHit/size=4096-4          224B ± 0%      155B ± 0%    -30.80%  (p=0.008 n=5+5)
CacheHit/size=0-4              0.00B         13.40B ±42%      +Inf%  (p=0.008 n=5+5)
CacheHit/size=16-4             0.00B          0.00B            ~     (all equal)
CacheHit/size=128-4            0.00B          0.00B            ~     (all equal)
CacheHit/size=512-4            0.00B          0.00B            ~     (all equal)
CacheHit/size=4096-4           0.00B          0.00B            ~     (all equal)
NoopStoragePar-4               0.00B          0.00B            ~     (all equal)
CacheStartupPar-4               267B ± 0%      282B ± 1%     +5.67%  (p=0.016 n=4+5)
CacheNoHitPar/size=0-4          232B ± 1%      162B ± 1%    -30.11%  (p=0.008 n=5+5)
CacheNoHitPar/size=16-4         228B ± 1%      161B ± 0%    -29.21%  (p=0.008 n=5+5)
CacheNoHitPar/size=128-4        229B ± 1%      162B ± 0%    -29.43%  (p=0.008 n=5+5)
CacheNoHitPar/size=512-4        228B ± 1%      162B ± 1%    -28.86%  (p=0.008 n=5+5)
CacheNoHitPar/size=4096-4       224B ± 0%      166B ± 0%    -26.02%  (p=0.000 n=5+4)
CacheHitPar/size=0-4           1.00B ± 0%    13.60B ± 4%  +1260.00%  (p=0.008 n=5+5)
CacheHitPar/size=16-4          0.00B          0.00B            ~     (all equal)
CacheHitPar/size=128-4         0.00B          0.00B            ~     (all equal)
CacheHitPar/size=512-4         0.00B          0.00B            ~     (all equal)
CacheHitPar/size=4096-4        0.00B          0.00B            ~     (all equal)
NoopStorageProc-4              0.00B          0.00B            ~     (all equal)
CacheStartupProc-4              269B ± 0%      285B ± 0%     +5.95%  (p=0.008 n=5+5)
CacheNoHitProc/size=0-4         240B ± 0%      194B ± 0%    -19.17%  (p=0.000 n=5+4)
CacheNoHitProc/size=16-4        240B ± 2%      194B ± 1%    -19.38%  (p=0.008 n=5+5)
CacheNoHitProc/size=128-4       241B ± 0%      193B ± 1%    -20.00%  (p=0.016 n=4+5)
CacheNoHitProc/size=512-4       241B ± 1%      188B ± 2%    -22.06%  (p=0.008 n=5+5)
CacheNoHitProc/size=4096-4      240B ± 1%      179B ± 0%    -25.52%  (p=0.008 n=5+5)
CacheHitProc/size=0-4          0.00B          3.60B ±17%      +Inf%  (p=0.008 n=5+5)
CacheHitProc/size=16-4         0.00B          0.00B            ~     (all equal)
CacheHitProc/size=128-4        0.00B          0.00B            ~     (all equal)
CacheHitProc/size=512-4        0.00B          0.00B            ~     (all equal)
CacheHitProc/size=4096-4       0.00B          0.00B            ~     (all equal)

name                        old allocs/op  new allocs/op  delta
NoopStorage-4                   0.00           0.00            ~     (all equal)
CacheStartup-4                  5.00 ± 0%      5.00 ± 0%       ~     (all equal)
CacheNoHit/size=0-4             3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHit/size=16-4            3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHit/size=128-4           3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHit/size=512-4           3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHit/size=4096-4          3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheHit/size=0-4               0.00           0.00            ~     (all equal)
CacheHit/size=16-4              0.00           0.00            ~     (all equal)
CacheHit/size=128-4             0.00           0.00            ~     (all equal)
CacheHit/size=512-4             0.00           0.00            ~     (all equal)
CacheHit/size=4096-4            0.00           0.00            ~     (all equal)
NoopStoragePar-4                0.00           0.00            ~     (all equal)
CacheStartupPar-4               4.00 ± 0%      4.00 ± 0%       ~     (all equal)
CacheNoHitPar/size=0-4          3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitPar/size=16-4         3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitPar/size=128-4        3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitPar/size=512-4        3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitPar/size=4096-4       3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheHitPar/size=0-4            0.00           0.00            ~     (all equal)
CacheHitPar/size=16-4           0.00           0.00            ~     (all equal)
CacheHitPar/size=128-4          0.00           0.00            ~     (all equal)
CacheHitPar/size=512-4          0.00           0.00            ~     (all equal)
CacheHitPar/size=4096-4         0.00           0.00            ~     (all equal)
NoopStorageProc-4               0.00           0.00            ~     (all equal)
CacheStartupProc-4              5.00 ± 0%      5.00 ± 0%       ~     (all equal)
CacheNoHitProc/size=0-4         3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitProc/size=16-4        3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitProc/size=128-4       3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitProc/size=512-4       3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheNoHitProc/size=4096-4      3.00 ± 0%      3.00 ± 0%       ~     (all equal)
CacheHitProc/size=0-4           0.00           0.00            ~     (all equal)
CacheHitProc/size=16-4          0.00           0.00            ~     (all equal)
CacheHitProc/size=128-4         0.00           0.00            ~     (all equal)
CacheHitProc/size=512-4         0.00           0.00            ~     (all equal)
CacheHitProc/size=4096-4        0.00           0.00            ~     (all equal)