Use 5G-S-TMSI as UE identity in RRCSetupRequest

This MR includes the following implementation:

• Handle 5G-S-TMSI in RRCSetup:

• Set the ue-Identity to ng-5G-S-TMSI-Part1 in RRCSetupRequest and
• If RRCSetup is received in response to an RRCSetupRequest: set the ng-5G-S-TMSI-Value to ng-5G-S-TMSI-Part2 in do_RRCSetupComplete

TS 38.331 5.3.3.3 Actions related to transmission of RRCSetupRequest message:

The UE shall set the contents of RRCSetupRequest message as follows:

1> set the ue-Identity as follows:

2> if upper layers provide a 5G-S-TMSI:

3> set the ue-Identity to ng-5G-S-TMSI-Part1;

• Pass 5G-S-TMSI to RRC when NAS receives GUTI in Registration Accept

• NAS extracts GUTI from Registration Accept
• send ITTI indication from NAS to RRC when GUTI is available and store 5G-S-TMSI in RRC instance

• Rework of Initial UE message handling in RRCSetupComplete: simplify code and memory management
• Fix for integrity failure after UE comes back from RRC IDLE
• Other NAS fixes

Note:

• Initial implementation of Initial NAS Message: Service Request -> moved to !3065 (merged)
• Rework of Registration Request added to !3176 (merged)

Closes #772 (closed)