Extract MediaRouter2Manager out of InfoMediaManager

This change abstracts router-related usages in InfoMediaManager using
the template pattern. It also creates ManagerInfoMediaManager as a
MediaRouter2Manager-based implementation of InfoMediaManager.

This is a non-functional change.

Test: atest InfoMediaManagerTest LocalMediaManagerTest
Bug: 192657812
Change-Id: I627f6d86ac3b36eb473575f717d9900fd782989f
6 files changed