Move NattKeepalivePacketData out of the framework

For implementing parcelable interface for NattKeepalivePacketData.
Move this class out of framework.jar and move to services.jar

This class is used in telephony-common.jar and it also loads
service.jar.

Bug: 33530442
Test: - build pass
      - atest NetworkStackTests
      - atest ConnectivityServiceTest

Change-Id: Ie1d02bb7bccb76415cf71824147466cabf6b88b6
Merged-In: Ie1d02bb7bccb76415cf71824147466cabf6b88b6
Merged-In: Idf7c25b6b553d8c0cc4ef2ea8193438480420fb4
(cherry picked from commit 58a1f931)