Copy MediaRouter2 tests into CTS

Changes from the original test files:
- Changed package names (android.media.cts)
- Renamed a test method (MR2Test#testControllers -> testGetControllers)
- Changed value of SAMPLE_PROVIDER_ROUTES_ID_PREFIX since package changed.
- Used androidx annotations

Bug: 148572935
Test: Passed following tests
      android.media.cts.MediaRoute2InfoTest
      android.media.cts.MediaRouter2Test
      android.media.cts.MediaRouterManagerTest
      android.media.cts.RouteDiscoveryPreferenceTest
      android.media.cts.RoutingSessionInfoTest
Change-Id: Ie2732635d542245dc37a3481d70893c2c6b79116