As with Radio Units organize a registry of cells and start to handle that
registry generally everywhere. Make parameters that configure cells, for
example tdd_ul_dl_config, dl_earfcn, bandwidth, pci, etc to be per-cell.

Cell registry is still populated from cell_list and slapparameter_dict.

Tests will be added later as full tests for generic MultiRU.

Rendered enb.cfg and gnb.cfg stay practically the same.

Backward compatibility: no change for ORS; For everything else cell parameters
stop to be global and are moved to cell_list.

--------

Appendix. Diff for rendered enb.cfg and gnb.cfg before and after this patch:

```
$ ./pythonwitheggs slapos-render-config.py && xdiff -w config/{old,out}
```

```diff
diff --git a/config/old/enb.cfg b/config/out/enb.cfg
index 5c6743c21..1b39f7044 100644
--- a/config/old/enb.cfg
+++ b/config/out/enb.cfg
@@ -1,6 +1,3 @@
-
-
-
 {
   log_options: "all.level=error,all.max_size=0,nas.level=debug,nas.max_size=1,s1ap.level=debug,s1ap.max_size=1,x2ap.level=debug,x2ap.max_size=1,rrc.level=debug,rrc.max_size=1,ngap.level=debug,ngap.max_size=1,xnap.level=debug,xnap.max_size=1,phy.level=info,file.rotate=1G,file.path=/dev/null",
   log_filename: "log/enb.log",
@@ -93,11 +90,11 @@
       srs_hopping_bandwidth: 0,
     },

-    drb_config: "drb",
+    drb_config: "default-drb.cfg",

     sib_sched_list: [
       {
-        filename: "sib",
+        filename: "default-sib23.asn",
         si_periodicity: 16,
       },
     ],
diff --git a/config/old/gnb.cfg b/config/out/gnb.cfg
index 6b04559c6..1fa637925 100644
--- a/config/old/gnb.cfg
+++ b/config/out/gnb.cfg
@@ -1,6 +1,3 @@
-
-
-
 {
   log_options: "all.level=error,all.max_size=0,nas.level=debug,nas.max_size=1,s1ap.level=debug,s1ap.max_size=1,x2ap.level=debug,x2ap.max_size=1,rrc.level=debug,rrc.max_size=1,ngap.level=debug,ngap.max_size=1,xnap.level=debug,xnap.max_size=1,phy.level=info,file.rotate=1G,file.path=/dev/null",
   log_filename: "log/enb.log",
@@ -77,7 +74,6 @@
     manual_ref_signal_power: true,
     ss_pbch_block_power: 8,

-
     tdd_ul_dl_config: {
       pattern1: {
          period: 5, /* in ms */
@@ -148,7 +144,7 @@
       ],
     },

-    drb_config: "drb",
+    drb_config: "default-drb.cfg",
   },
   ],
   nr_cell_default: {
```