Filter memory tombstone fields before DropBox logging

Introduced ProtoFieldFilter utility to filter specific fields from ProtoInputStream, added methods in BootReceiver to filter the unused memory mapping scections from tombstone files before adding them to dropbox, and modified NativeTombstoneManager to handle proto tombstones based on the new proto_tombstone flag.

Bug: 323857385
Flag: com.android.server.os.proto_tombstone
Test: atest ProtoFieldFilterTest && manual workflow verification
Change-Id: Iccab764656bf2ee6977e3f0eb74c8f5f6fb0308e