Reformulate section on standalone mode

Clarifications on when (or if) to use --sa

Add note to 'doc/README.md' to insight readers to checkout the documentation at their version of the repository.

Add notes around sample SA gNB and nrUE commands in most basic tutorials 'NR_SA_Tutorial_COTS_UE.md' and 'NR_SA_Tutorial_OAI_nrUE.md'.
The notes mention that for versions previous to 2024.w45, the --sa argument should be added to run in SA mode.

Integration: `2024.w46`

See merge request oai/openairinterface5g!3106

* !3095 UE: Set default SSB config
* !2991 fix BSR report malformed, add SHORT BSR when it can (instead of LONG BSR)...
* !3104 Trigger deregistration only in SA mode → small fixup?
* !3107 Clip the input for -32768 because this will make different result in...
* !3109 T tracer: support float types in traces
* !2777 NR UE trigger for re-establishment
* !3108 Prevent segfaults in gNB stack
* !3059 Test for init_RA
* CI: increase UE thread pool size
* !3036 Further improvements in analog beam management for CSI-RS
* !3093 Added NTN FDD FR1 bands defined in 3GPP TS 38.101-5

Added NTN FDD FR1 bands defined in 3GPP TS 38.101-5

Added support for NTN FDD FR1 bands 254, 255, 256 as specified in 3GPP
TS 38.101-5. Example Conf files added for band254 for 15Khz, 5Mhz and
30Khz, 10Mhz configurations. Tested NTN GEO configuration on band 254
using these conf files.

Merge remote-tracking branch 'origin/enabling_CSIRS_analog_beamformiing_l1_handling' into integration_2024_w46 (!3036)

Further improvements in analog beam management for CSI-RS

There seem to be randomly occurring deadlocks when running the UE in the
CI. MR !3091 should fix this. While waiting for this, apply a workaround
by increasing the number of worker pools in the UE to 12.

Since tag 2024.w45/commit f54ca571,
standalone mode/--sa is the default and does not exist. Correspondingly,
it has been removed from the documentation.

For users reading recent documentation, but running an older version of
OAI, there might be a mismatch in that --sa is necessary to run OAI, but
not given in the documentation. Provide explanatory text to make users
aware of this.

Test for init_RA

A testcase for init_RA function.
The testcase redefines the following functions as stubs:

- nr_mac_rrc_ra_ind
- nr_write_ce_ulsch_pdu
- mac_rlc_data_req
- lockGet_ul_config
- release_ul_config
- remove_ul_config_last_item
- nr_ue_configure_pucch

These stubs can be used to check init_RA behavior

Prevent segfaults in gNB stack

Three fixes for segfaults, discovered while running with many UEs.
See commit messages for more details.

Merge remote-tracking branch 'origin/NR_UE_trigger_reestablishment' into integration_2024_w46 (!2777)

NR UE trigger for re-establishment

The implementation in this MR triggers RRC re-establishment at the UE in case
of radio link failure either for out of sync messages from lower layers or in
case maximum number of RLC retransmissions is reached.

/opt/oai-gnb/bin/nr-softmodem -O /opt/oai-gnb/etc/gnb.conf --sa --log_config.global_log_options level,nocolor,time --rfsimulator.options chanmod --telnetsrv --telnetsrv.listenaddr 192.168.71.150 --telnetsrv.shrmod ci
=================================================================
==7==ERROR: AddressSanitizer: odr-violation (0x7fce78b85be0):
  [1] size=4 'log_mem_write_side' /oai-ran/common/utils/LOG/log.c:78:14
  [2] size=4 'log_mem_write_side' /oai-ran/common/utils/LOG/log.c:78:14
These globals were registered at these points:
  [1]:
    \#0 0x7fce7b691658 in __asan_register_globals ../../../../src/libsanitizer/asan/asan_globals.cpp:341
    \#1 0x7fce7bd0c47d in call_init elf/dl-init.c:70

  [2]:
    \#0 0x7fce7b691658 in __asan_register_globals ../../../../src/libsanitizer/asan/asan_globals.cpp:341
    \#1 0x7fce7a5e2eba in call_init ../csu/libc-start.c:145
    \#2 0x7fce7a5e2eba in __libc_start_main_impl ../csu/libc-start.c:379

==7==HINT: if you don't care about these errors you may set ASAN_OPTIONS=detect_odr_violation=0
SUMMARY: AddressSanitizer: odr-violation: global 'log_mem_write_side' at /oai-ran/common/utils/LOG/log.c:78:14
==7==ABORTING
[INFO  tini (1)] Spawned child process '/opt/oai-gnb/bin/entrypoint.sh' with pid '7'
[INFO  tini (1)] Main child exited normally (with status '1')

* trigger re-establshemnt on DU: reset RLC counters on DRB 1
  for OAI UE, since SRB 1 does not work for lack of periodic
  measurements reports
* how is the re-establishment triggered?
  * a transmission on DRB 1 occurs
  * detection of a mismatch of RLC counters at the UE side
  * max number of RLC retransmissions reached
  * RLF detection
* verify re-establishment on CU: we ping the core from the UE; this
  sends packets on DRB, and because the sequence number mismatches, will
  trigger a reestablishment. We accept in the ping that a couple of
  packets might be lost; after ping is over, reestablishment must be
  done as well (else the ping will already fail).

Clip the input for -32768 because this will make different result in...

Clip the input for -32768 because this will make different result in
mult_complex_vectors() compared to C version

T tracer: support float types in traces

Trigger deregistration only in SA mode

Upon press of ^C, the UE triggers a NAS deregistration. This does not work
in do-ra or phy-test modes, because there is no NAS. Therefore, in non-SA
modes, just stop the UE directly.

This can potentially improve the 5G RFsim CI test case, because together with
a high RFsim timeout, the chances of the last HARQ status line being without
retransmissions is much higher. If that does not help, we can further increase
the retx threshold.

fix BSR report malformed, add SHORT BSR when it can (instead of LONG BSR)...

fix BSR report malformed, add SHORT BSR when it can (instead of LONG BSR)
simplify the code and make the code more explicit, but the may structure
remain (nr_write_ce_ulsch_pdu interface is complex, merging it into the
called would make simpler and more interstandable code), fix some asserts
related to this part of code

Similar to the previous commit, prevent the same segfault in RRC.

Added support for NTN FDD FR1 bands 254, 255, 256 as specified in 3GPP TS 38.101-5
Conf files added for 15Khz, 5Mhz and 30Khz, 10Mhz configurations added for these bands

In some runs of a multi-UE deployment, we see segfaults because
cell_group->spCellConfig is NULL. We should not segfault in that case,
so check for spCellConfig.

When the UE list is full, the iterator will run through all
MAX_MOBILES_PER_GNB UEs. It expects that eventually the pointer is NULL,
which is not the case if we have MAX_MOBILES_PER_GNB (or it simply
depends on the following memory). So give one array entry more, to
ensure that the last one is NULL.

Clip the input for -32768 because this will make different result in mult_complex_vectors() compared to C version