Previously RU type was static parameter of particular software - it was
possible to instantiate cells only with selected RU type for particular template.

In MultiRU it will be possible to generally instantiate all kind of cells -
LTE/NR and TDD/FDD all at the same time and each served by a different kind of Radio Unit.

-> Switch RU to be runtime parameter as a preparatory step for that.

There is now only two software releases:

  - ORS (software-ors.cfg), and
  - generic (software.cfg).

ORS behaviour stays the same as before here by patch.

For generic each cell in cell_list now needs to explicitly specify which kind
of RU it wants to use and with which parameters. There are less defaults: for
example which CPRI board and SFP port to use now needs to be explicitly
specified.

Only ORS tests are left for now. The old test{LOPCOMM,M2RU,ANY} did not
exercised any driver-specific functionality and until recently were not run at
all due to '-' in their file name. We remove them for now and we will add tests
for generic in a soon follow-up patch after switching LTE/NR cell type to also
be a runtime parameter.

Backward compatibility:

  * nothing changes for ORS
  * for generic all RU-related parameters are now moved from cell_list to
    cell_list.ru, there are several renames and besides ru_type ru_link_type also
    needs to be specified. Please see new RU-related JSON schemas added into
    ru/ for details. Cell_list itself now also does not provide a default with
    one cell - if no cells are configured no cells are instantiated.

--------

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 1b39f7044..89862f1d9 100644
--- a/config/old/enb.cfg
+++ b/config/out/enb.cfg
@@ -6,7 +6,7 @@

   // Radio Units
   rf_driver: {
-      // default-RU 2T2R  (ors)
+      // CELL-RU 2T2R  (sdr)
       name: "sdr",
       args: "dev0=/dev/sdr0",
       rx_antenna:"tx_rx",
@@ -27,7 +27,7 @@
   // LTE cells
   cell_list: [

-    // default  (default-RU)
+    // CELL  (CELL-RU)
     {
       rf_port:      0,
       n_antenna_dl: 2,
@@ -90,11 +90,11 @@
       srs_hopping_bandwidth: 0,
     },

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

     sib_sched_list: [
       {
-        filename: "default-sib23.asn",
+        filename: "CELL-sib23.asn",
         si_periodicity: 16,
       },
     ],
diff --git a/config/old/gnb.cfg b/config/out/gnb.cfg
index 05deb5ada..1df699a22 100644
--- a/config/old/gnb.cfg
+++ b/config/out/gnb.cfg
@@ -6,7 +6,7 @@

   // Radio Units
   rf_driver: {
-      // default-RU 2T2R  (ors)
+      // CELL-RU 2T2R  (sdr)
       name: "sdr",
       args: "dev0=/dev/sdr0",
       rx_antenna:"tx_rx",
@@ -35,7 +35,7 @@
   // NR cells
   nr_cell_list: [

-      // default  (default-RU)
+      // CELL  (CELL-RU)
       {
         rf_port:      0,
         n_antenna_dl: 2,
@@ -136,7 +136,7 @@
           ],
         },

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