Fix permission checking for a11y volume.

Adding new permission for changing accessibility volume
to allow system UI to change it. Also providing audio
manager with a whitelist of bound accessibility service
uids so it can allow servics to change the volume.

Bug: 36569297
Test: Adding CTS test in linked CL.
Change-Id: I4f327e3a251fc3780c5957f41217c2ef5bb8b16e