Merge changes from topic "cherry-pick-cell-keepalive"

* changes:
  Rework KeepalivePacketData for Compatibility with Cell
  Add Constants for NATT Keepalive to RILConstants
  Relocate KeepalivePacketData to frameworks/base
tree: 4416dfcf3ada0ba7591cac8084e063e658936f75
  1. core/
  2. services/
  3. tests/