The code is forced to use nea2, no matter what the UE supports.

After 2^18 PDCP packets, it will fail to work (we don't use HFN yet).

These limitations will be fixed in later commits.

The existing security function was not reused, because it does too
much memory allocation and initializes the security context at each
ciphering. So here comes nr_pdcp_security_nea2_cipher(). And also
the ciphering is done inplace. To be changed if necessary.

This reverts commit 15caed4d.

- do DRB preconfiguration for deafult C-RNTI if !do_ra
- moved redundant configuration code at RLC layer to new RLC functions

Add rrc_gNB_process_NGAP_PDUSESSION_RELEASE_COMMAND and rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE

Add rrc_gNB_send_NGAP_PDUSESSION_SETUP_RESP
Fix some problems about pdu session setup

Modify SecurityModeFailure