Disambiguate between unique and original ids in MR2Provider

There are still uses that don't have the disambiguation, but MR2Provider
is the root of trouble for the use of ids in transfer reason assignment.
We can propagate this disambiguation further in following CLs.

Test: atest CtsMediaBetterTogetherTestCases CtsMediaHostTestCases
Flag: com.android.media.flags.enable_built_in_speaker_route_suitability_statuses
Bug: b/319651986
Change-Id: I23aef4ec28683fa6e4eafd9311daac55cec760d7