Extract interface from QuickSettingsController

Extracts an interface that exposes all methods in QsController that are used outside of NPVC, and deprecates most of them.

Bug: 327643166
Test: Manually verified QS functionality is unchanged
Test: Manually verified Flexiglass doesn't crash when turned on
Test: Passes existing tests
Flag: NONE
Change-Id: If4a84a3d9c2fdd5b3c5fc5287c6cc61bd4ccd91c