[2/2] Use static singleton AudioManagerRouteController

This change makes the output audio routing HSUM compatible.

Design doc: go/mr2-hsum-compatible

Change-Id: Ib9c3b72d4b333e9e2e057fa4257d21945fb3ecd8
Bug: b/372868909
Test: locally
Flag: com.android.media.flags.enable_use_of_singleton_audio_manager_route_controller