Refactor Global Mic Disable

This CL changes the setting propagation of the user microphone
privacy setting to imply if CHRE can access the microphone, as
opposed to piping down the raw setting.

Bug: 183416485
Test: Toggle the setting, verify that the setting change notification
is handled as expected, toggle the microphone privacy setting to
verify correct behavior.

Change-Id: I1cbbe6cc6312ed91eba15759836e588b4cd70cad