Refactor RoutingCoordinator

- This CL puts RoutingCoordinator into staticlibs to make it usable by
both Tethering and ConnectivityService on R.
- This CL also changes the return type of
  ConnectivityInternalApi#getRoutingCoordinatorManager() to IBinder so
  it has fewer dependencies.

Bug: 350699020
Test: CI

Change-Id: Iba096e940795cd33e61c5141721394ad39e5ce6d
14 files changed