AudioAttributes: test API for injecting a test identifier

Add a test API for supporting adding an identifier inside
the AudioAttributes. It is stored inside the associated Bundle.

When creating an anonymized copy of an AudioPlaybackConfiguration,
also copy the test identifier if present (and ignore the other
contents of the Bundle).

Bug: 410700323
Flag: EXEMPT bug fix
Test: atest android.media.audio.cts.AudioPlaybackConfigurationTest
Change-Id: I92ca0eaf4b8264a9439b3846fa6363bc17fa7e57