Deprecate unused methods in QSTileImpl

* Deprecate getMetricsCategory, as UiEvents just use a string for each
tile.
* Remove all a11y announcements methods. These were not used, as we've
been using stateDescription

Test: atest SystemUITests
Bug: no bug

Change-Id: Id7a53abe59bc2b265f3049e844d9e8d9c4ef1f83