Add method to check if streams can be muted from UI

The new method returns false for STREAM_VOICE_CALL and
STREAM_BLUETOOTH_SCO. They should never be muted by users.
There are only few cases where this is allowed.

Flag: EXEMPT bugfix
Test: manual
Bug: 349592304
Bug: 349604691
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:fb8a06942429934fe697ba05a5b5b0523f5e3b14)
Merged-In: Ia312b59bd846190e433ca22de6fe49e5f4f4b0a0
Change-Id: Ia312b59bd846190e433ca22de6fe49e5f4f4b0a0