Remove user id based audio captured API.

Removed recently added user id based routing for audio playback capture.
The original goal of the user id based routing was for the routing to be
controlled by audio policy and to controll where audio from a user
could play. The audio playback capture was added to match similar API
provided for audio playback capture based on application's uid.
Currently, there is no appropiate use case for capturing based on user
id. While this could prove useful in the future the appropiate use case
research must be completed. Updated comments for audio policy user id
based routing.

Bug: 149419551
Test: atest AudioPlaybackCaptureTest
Test: atest
com.google.android.gts.audio.AudioHostTest#testUserIdDeviceAffinity

Change-Id: I174cba618c4f66d11185e7ab5630094b4a8cb35b