Add flag for exclusive focus muting notifications when recording

Legacy behavior is to mute notification while an app has
requested audio focus with GAIN_TRANSIENT_EXCLUSIVE.
The new flag is to enforce that the muting happens only
when the focus requester is also recording audio.

Flag: android.media.audio.focus_exclusive_with_recording
Test: atest android.media.audio.cts.AudioFocusTest
Bug: 316414750
Change-Id: I8547ff735267158a65282134e60fa97f94b5f2a8