Add methods to get vendor extension interfaces

Add the following methods to TvInputManager.

 - Method to get the list of vender extension interfaces
 - Method to get the interface from the list

Bug: 193052431
Test: run cts -m CtsTvTestCases -t
android.media.tv.cts.TvInputManagerTest

Change-Id: Ia2c88f6cc57f2af3cf00d27e1c7e0224a563b595