library/GSM_RR_Types: add minimalistic AssignmentCommand

Unfortunately, the existing implementation [1] is somewhat
incomplete and unfriendly to build templates on:

  - some fields holding integer numbers defined as BITx,
    so we would have to do bit2int() / int2bit();

  - some bit-map fields defined as octetstrings;

  - some fields are not decoded at all (raw octetstrings).

Let's work this around by defining a minimalistic implementation
of (RR) Assignment Command with all mandatory and some optional
fields.  Reuse some IEs directly from MobileL3_RRM_Types.

[1] titan.ProtocolModules.MobileL3_v13.4.0
    MobileL3_RRM_Types.PDU_RRM_AssignmentCommand_NW_MS

Change-Id: If1a5244a688abed6e6de2bf3f6e19e0e28129ea5
Related: SYS#4868, OS#4545
2 files changed