integration_2021_wk51_d_2 (done on 2022_wk01)

MR !1274 : L2 Emulator for NSA Mode
This merge request will incorporate the NSA UE with the L2 Emulator (bypassing of layer 1). 
These changes include the following features:

-NSA Interface between LTE and NR UE is properly established. These include the following steps: 
 First UE capability enquiry is sent to NR UE 
 NR UE updates and fills first capability enquiry
 eNB request for a measurement report
 Measurement request is sent to NR UE
 Measurement report is filled in NR UE
 Measurement report is received in eNB
 Request for second UE capability enquiry
 Send second enquiry to NR UE
 Second capability information is filled by NR UE
 Second capability information is sent to eNB
 NR UE capability information is received in gNB
 Periodic measurement report received in gNB
 RRCReconfigurationRequest is sent to NR UE
 RRCReconfigurationComplete is sent from NR UE
 RACH is received in the gNB
 RAR is received in NR UE
 Msg 3 is generated and sent to gNB
 CFRA procedure is complete

-A single NSA UE is able to ping an external source
-UE-to-UE traffic is still in work
-The gNB is crashing regularly and is still in work

MR !1265 : F1 split for 5G 
documentation in doc/f1.md 
Use new gtp-u for also 4G (no legacy code cleanup, will be done after this MR) 
Some various fixes in the existing code when we face issues 4G F1 behavior will also change