Automatically add FEATURE_IPSEC_TUNNEL_MIGRATION for U/U+ devices.

This change automatically enables the IPSEC_TUNNEL_MIGRATION
feature if the VSR API level is greater than T

This is for OEM convenience to ensure that they do not have to add the
feature for each device that they ship.

Bug: 169169973
Test: Removed feature from device, CTS tested on sunfish that
      the feature does not exist
Change-Id: I4ddaa8803be6e9738a2bd0af6793720571b67ff2