TestableNetworkCallback will become a standard tool. This patch
and its companion in packages/modules/NetworkStack mostly move
it out of ConnectivityServiceTest, but also applies a few
cleanups like reordering arguments for standard order, renaming
...Like to ...That to match Mockito namings, and introduces
stonger static typing on some callbacks, which allows to remove
some unchecked casts.
Test: atest FrameworksNetTests NetworkStackTests
Change-Id: I808a95ac33ec0c81a8829cad36a6917524297574
9ce1e28788