Merge "Resolve 3 inconsistencies in accessibility button API - Unify logic for...

Merge "Resolve 3 inconsistencies in accessibility button API - Unify logic for detecting availability of the accessibility button - Ensure the initial visibility state is propagated to A11yMS - Ensure services only receive availability callbacks for changes" into oc-dev am: 4ab690a5 am: 8097485c
am: 8cc3fee9

Change-Id: Iae4767d6d764f272c3c867276483f7f8522259fe