Contributions by Robert Schmidt <robert.schmidt@openairinterface.org>

Merge remote-tracking branch 'origin/NR_RRC_config_improvements_multi_UE' into integration_2023_w18b

Different threads (e.g., RRC, DU tasks) might access the scheduler at
the same time as the thread that drivers the scheduler itself
(ru_thread). To avoid data races, introduce this mutex.

Most functions of the scheduler are only used internally and have been
marked static in the previous commit. The remaining ones, in this
commit, either lock the scheduler mutex sched_lock, or a comment has
been added of the assumption of how such function is to be locked (e.g.,
if it might be called from different places, or if it is called by a
function that already locks the scheduler).

There is no point in updating RA, when we update the CellGroupConfig. We
simply drop this function, therefore

To know which functions are used from outside and which are
module-local, make many functions static. This will allow us to protect
only those functions with a mutex for which it is necessary.

The CellGroupConfig should come from the DU. Currently, any update made
to the CellGroupConfig is done at CU. In split-operation, we have no way
of telling the DU about this update. Hence, in this commit, check if we
are in F1 split mode operation during a CellGroupConfig update, and if
so, suppress any updates to the CellGroupConfig, alongside a warning.

integration_2023_w17

See merge request oai/openairinterface5g!2083

* !2045 ssb offset to point A harmonization
* !2068 Add mac_CellGroupConfig in RRCReconfiguration after a RRCReestablisment
* !2052 fix(ci): for old versions of iperf, server process shall be killed manually
* !2056 Generic changes related to UEs used in CI
* !2074 Fix of command for USRP B200 reset in CI pipeline
* !2014 transform global variables into const or static
* !2082 Change of the PLMN in AW2S pipeline
* !2078 Improve PRS Tutorial
* !2079 Update scope (Xforms, Qt) documentation and list in doc/README.md

Merge remote-tracking branch 'origin/Fix_mac_CellGroupConfig_after_reestablishment' into integration_2023_w17