Merge changes from topic "keepalive-on-cell"

* changes:
  Rework KeepalivePacketData for Compatibility with Cell
  Add Constants for NATT Keepalive to RILConstants
  Relocate KeepalivePacketData to frameworks/base
tree: 5d71ae7d508d4d1bb1c1a453a3353075233c4ddc
  1. core/
  2. services/
  3. tests/