This commit introduces an additional (implicit) option that signals if
the E2 agent is to be activated or not. When reading the configuration,
we now check if all fields are set, and activate the E2 agent only if
this is the case. If not, we only print a warning and start the gNB
without the agent.

Note that previously, if not all fields are set correctly, the gNB
stopped.

To implement this behavior, it is necessary to change the defaults of
the RIC IP and the directory for SMs to a (non-NULL) default value.
Otherwise, the configuration system would not consider the field to be
set to the default, and wrongly assumes the field is set, even though it
is not; at least, this change is necessary to make config_isparamset()
return NULL if the configuration is not set.

3GPP has the concept of a gNB-CU-UP ID and a (separate) gNB ID (for gNB,
CU-CP). This commit introduces the gNB-CU-UP as a separate ID that has to be
set in the configuration file when running as a CU-UP. For the
CU/monolithic gNB, it is optional (but needs to be the same as the
gNB-ID if specified).

The CU-UP ID is necessary, as some entities, e.g., the e2 agent, need to
signal both IDs, e.g., to reconcile a CU-CP and (multiple) CU-UP(s)
belonging together.

3GPP has the concept of a gNB-DU ID and a (separate) gNB ID (for gNB,
CU). This commit introduces the gNB-DU as a separate ID that has to be
set in the configuration file. It is necessary, as some entities, e.g.,
the e2 agent, need to signal both IDs, e.g., to reconcile a CU and
(multiple) DU(s) belonging together.

See merge request oai/openairinterface5g!2450

* !2440 hotfix: set PDCP t-reordering to 100ms
* !2439 rfsimulator: ignore PIPE signal
* !2441 minor: documentation: advertise correct default value for --ssb
* !2446 chore(ci): displaying the ASN1C commit
* !2443 CI documentation: updates and how to reproduce
* !2355 NR UE improve handling of MSG4 feedback in default PUCCH
* !2408 NR UE MAC config improvements
* !2431 T: isolate generated .h files when using make
* !2442 nr pdcp: rework reestablishment
* !2448 lte: switch to RRC release 16.13.0
* !2088 Implementation of logical channel prioritization at UE
* correctly read timing advance option `-A` in gNB
* set sample advance for OAIUE test to make it more stable
* set gain for OAIUE test to make it more stable
* !2445 Correctly allocate SCC n_TimingAdvanceOffset
* !2454 bugfix: fix NSA CI test

It seems like initialDLBWPcontrolResourceSetZero needs to be set
otherwise the quectel UE does not accept the Reconfiguration.

Merge remote-tracking branch 'origin/implement_logical_channel_prioritization_ue' into integration_2023_w47

A COTS UE is sending UE capabilities with accessStratumRelease "rel16"
which is not decoded by our RRC. Switching to RRC 16.13.0 lets our RRC
accept these capabilities (and as a positive side effect lets this
particular UE work nicely in NSA fr1).

Merge remote-tracking branch 'origin/NR_UE_improve_handling_msg4_feedback' into integration_2023_w47

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

cleanup means:
- typo: susbend -> suspend
- call nr_pdcp_manager_unlock() where needed
- simplify LOG_XX (remove __FILE__, __LINE__, __FUNCTION__)

note:
nr_pdcp_release_srb() and nr_pdcp_release_drb() don't use
nr_pdcp_release_drb() because they modify the arrays, so
it does not make sense to "abstract" the accesses to
->srb and ->drb.