Fix OAI UE memory leaks
Fix 1: Replaced asn1cFreeStruc with ASN_STRUCT_FREE in MAC layer to properly
free nested ASN.1 structures in cell group configuration.
Fix 2: Removed premature nullification of dedicatedNAS_Message->buf in
dlInformationTransfer processing to allow proper ASN.1 cleanup.
Fix 3: Fixed memory ownership in nr_rrc_process_dedicatedNAS_MessageList by
copying OCTET_STRING data instead of transferring ownership, preventing
ASN.1 cleanup from losing track of allocated memory
Closes#828