Paging (RRC/ASN): refactor do_NR_Paging and extend UE identity support

Replace the old buffer-based do_NR_Paging API with a params struct and
byte_array_t return; add support for fullI-RNTI and optional accessType/
pagingCause. Encoding uses uper_encode_to_new_buffer, callers own and
free the returned buffer.

Changes:
- asn1_msg.h:
  - Add nr_paging_params_t (ue_identity_type, union ue_identity union
    { m_tmsi or full_i_rnti }, access_type, paging_cause),
  - Add NR_PAGING_FULL_I_RNTI_SIZE define.
- asn1_msg.c:
  - Implement do_NR_Paging with nr_paging_params_t.
  - Support ng-5G-S-TMSI (48-bit, M-TMSI in bytes 2–5)
    and fullI-RNTI (40-bit, 5 bytes).
  - Set optional accessType (non3GPP) and optional nonCriticalExtension
    (pagingRecordList-v1700 with pagingCause-r17).
  - Use asn1cCalloc for ASN.1 allocations and encode via
    uper_encode_to_new_buffer. On failure free buffer and return empty
    byte_array_t.
- rrc_gNB.c: disable do_NR_Paging call in rrc_gNB_generate_pcch_msg
  with #if 0 (will be removed in a descendant commit, no need to update
  call site yet).
- test_asn1_msg.cpp: update caller in asn1 tests (minimal change, test
  will be updated in a later commit)
- common/platform_constants.h: add NR_PCCH_MAX_PAGING_RECORDS

Signed-off-by: Guido Casati <guido.casati@openairinterface.org>

common/platform_constants.h

@@ -71,6 +71,9 @@
 // SDAP
 #define MAX_QOS_FLOWS 64
 
+/** Maximum number of PagingRecords in one PCCH Paging message (TS 38.331) */
+#define NR_PCCH_MAX_PAGING_RECORDS 32
+
 // SDAP/5G NAS NOS1
 #define DEFAULT_NOS1_PDU_ID 10