Rollback chooser menu to version Q behavior for accessibility button (2/n).

Allow separate Activities to handle the multiple-target case for the hardware and software shortcuts. Migrate from an extra to an explicit class so the Intent dispatch will launch the correct Activity for the particular shortcut.

Bug: 151294664
Test: manual test
Change-Id: I54bb1d3ab91e2757c465e8763786d0234f6d4ea8