Integration PHY and MAC procedures for Timing Advance updates. Compilation and run is OK. TA updates need further fixes as not working as expected.

- "nr_process_timing_advance": TA to be applied is commented out, need to be uncommented
- with introduced delay of 50 in rx_rf, TA update should be 34 in MAC CE
  but this does not occur when ta is applied at UE side according to standard
- introduced ULSCH scheduler and NR RX SDU functions
- fixes to logic in UL fill RX indication
- added crc indication in UL RX
- temporary hardcoded UE_id to 0, rnti not considered in the logic

- Initial gNB DLSCH and UE spec scheduling implentation
- MAC PDU generation (including header as per TS 38.321)
- MAC PDU processing at UE side with extracion of TA updates
- General code cleanup
- Introduced NR MAC COMMON folder, moved common files here

Fix usrp_lib for threequarter sampling

See merge request oai/openairinterface5g!732

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

Integration develop nr 2019w48bis

See merge request oai/openairinterface5g!729

Signed-off-by: Prateek Bidwalkar <prateek.bidwalkar@ipaccess.com>

Signed-off-by: Prateek Bidwalkar <prateek.bidwalkar@ipaccess.com>

Develop nr fix multi rru

See merge request oai/openairinterface5g!722

Nr channel estimation and other fixes

See merge request oai/openairinterface5g!714

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

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

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

Integration develop nr 2019w46

See merge request oai/openairinterface5g!716

Merge remote-tracking branch 'origin/fix-nr-rfsim-gNB-notx-slots2to19' into integration-develop-nr-2019w46

Merge branch 'nr-channel-estimation' of https://gitlab.eurecom.fr/oai/openairinterface5g into nr-channel-estimation

In 3/4 sampling mode, the OFDM symbol size is _not_ a power of two (e.g. 1536 instead of 2048).
In this case it is _not_ OK to calculate the modulus using a binary AND, it _must_ use either the actul modulus operator (%) using an integer division,
or a _correct_ if statement or tertianary operator like this:

re_offset = (re_offset + 4 >= ue->frame_parms.ofdm_symbol_size) ? (re_offset + 4 - ue->frame_parms.ofdm_symbol_size) : (re_offset + 4);

But of course using the actual modulus operator is much more readable and surely not much slower:

re_offset = (re_offset + 4) % ue->frame_parms.ofdm_symbol_size;