MR957 : rlc v2: implement SOstart/SOend in NACK reporting

If we NACK without SOstart/SOend then the other end of the RLC channel will consider all the bytes as NACKed and will have to resend them all. 
If another status is then reported before all the bytes are sent, and because we don't use SOstart/SOend this status will NACK all the bytes again, then all the bytes are to be sent again. 
And the cycle repeats. It will end with a max retx reached (which triggers RLF, Radio Link Failure).

MR1010 : NR UE: Fix for error message - no active DLSCH
- Fixes for the following error message at UE: [PHY] [UE][FATAL] nr_slot_rx 1: no active DLSCH

MR994 : Cleanup softmodem main
- Introduces --dlsch-parallel command line option to set the number of threads for dlsch decoding. If set to 0 (default) no parallelization. 
- Some cleanup in tracing and in nr-uesoftmodem.c data.

MR999 : NR FR2 RA
- Temporary Fix of RA procedure for FR2 (both gNB and UE)
- Fixes in gold sequence initialization at UE
- Moves 2nd downlink to slot 3 instead of 2 to avoid clash with UL DCI (only 1 candidate per slot in FR2 currently)

MR988 : SIB1
Initial implementation of SIB1