Closes #762

Explanations: see #706. TLDR: the RRC code calls nr_pdcp_remove_ue(), so
we should not call it in the E1 handler if we do not use split mode.

From 3GPP TS 38.321 Section 5.4.3 Multiplexing and assembly, we need to process the highest priority subPDUs first:
- MAC CE for C-RNTI is the one with higher priority

DCI formats 11 and 01 assume the presence of an active BWP, if not present return with an error to prevent segfault

demoting to LOG_D another log that otherwise would be printed too many times at the UE because of periodic calling of to_nrarfcn

fix ug on pilot 2 in nr_pbch_dmrs_correlation() that is lacking signal processing, make the code in pbch simpler and faster

  - hardcoded data for E2 Setup Request; fill_rnd_data_e2_setup_req.c dependancy taken
    out

  - RAN Function Definition implemented
  - use mutual E2SM UE ID file
  - write_ctrl_rc_sm function cleanup

  - RAN Function Definition implemented
  - ran_func_kpm.c - use function pointers based on the matching condition,
    and node type
  - ran_func_kpm_subs.h/c - for measurement collection within
    MAC/RLC/PDCP layers; for CU-UP node only PDCP included (otherwise,
we would get undefined reference to MAC/RLC)
  - use mutual E2SM UE ID file

improvements in Bj computation and implementing a timer to compute time elapsed since last Bj update

Co-authored-by: Robert Schmidt <robert.schmidt@openairinterface.org>

In phy-test, the scheduler has a hardcoded UE allocation; if CQI and RSRP
are not evaluated, there is no change in the scheduler function. Also,
this avoids misleading error messages if no UE is connected.

Use the correct function in order to close open RFsim connections,
instead of a simple close(). If this is not done correctly, it might
happen that the softmodem closes, but an L1 thread might still read
samples (bug in higher layers). Then, RFsim tries to read a socket
(because it has an open connection), but the actual connection had been
close()d. This commit fixes this behavior.