Add API for apps to check if they are the network owner

This CL extends NetworkCapabilities#mEstablishingVpnAppUid
to the network owner app UID and introduces a new public API
to get this owner app's UID.

Bug: 142072839
Test: atest FrameworksNetTests
Change-Id: Id83cdea62b89b586aff74e51e3fee60e53d37d4c
4 files changed
tree: 5c1fd6476cdbf4a7a8ad93be90093c53516e3889
  1. core/
  2. services/
  3. tests/