- Remove any FlexRAN code
- Cleanup config files
- Remove LFDS7, libyaml dependencies

- AssertFatal() in nr_rlc_srb0_recv_sdu() if the srb0 is not found
- do_RRCSetup() may return -1, handle it properly
- do_RRCReject() may return -1, handle it properly
- remove one switch in rrc_gNB_generate_RRCReject()

If we do not stop RF after all threads, it can happen that the RF is
finished, but another thread of the RU (e.g., reorder thread) tries to
send out a package to the RF. This can lead to a segfault, as observed
in UHD, because we free all resources before reusing them.

This commit fixes this behavior.

Using Accelleran CU, the DRB ID is 4 (not 1), we need to set and access
the array 'drb_priority' correctly in the DU specific functions.

Before this commit, we had the following error:
[NR_MAC]   ASN1 message CellGroupConfig encoding failed (rlc-BearerToAddModList, 18446744073709551615)!

- Refactor iperf analysis into IperfAnalyze function
- IperfAnalyze uses server report, or uses last client report (for MBMS
  case)
- Additional check: duration as recognized in server/client report is
  according to command line