Rename AudioPoliciesBluetoothRC to BluetoothDeviceRoutesManager

For two reasons:
- Removes the RouteController prefix (this class doesn't implement
  the BluetoothRouteController interface).
- Removes the AudioPolicies prefix (unrelated to the class).

Bug: 205124386
Test: atest MediaRouterServiceTests
Change-Id: Ibb4e53b846ef69582d92653e095c31084cfb0df3