Add Multi-PLMN and CSG support

Non-functional changes:
-Clarify that the MCC+MNC in the CellIdentity should be used to
 report the Primary PLMN only; (this PLMN is globally unique, and
 can be used to construct a CGI/ECGI whereas other PLMN-IDs cannot).
-Add clarification for the reporting of multi-PLMN 5G networks.

Functional changes:
-Add a list of PLMNs for MOCN Networks. This allows cells that are
 shared by multiple operators to be properly reported.
-Add support for Closed Subscriber Group reporting to allow
 identification of small-cell deployments.

Bug: 135921133
Test: make VtsHalRadioV1_5Target
      && make aosp_cf_x86_64_phone-userdebug
Change-Id: Ibb0682de8ae9c4421e79086773c977a4e76ac4f1