Revise Accessibility button chooser intent/permissions

1) Switch AccessibilityButtonChooserActivity to non-exported
2) Update AccessibilityButtonChooserActivity's intent action to
   be CTS-compliant
3) Switches to correct permission to validate a click of the
   accessibility button originated from the status bar service

Bug: 36866328
Bug: 36976440
Test: Manual / Created app to validate launch protection
Change-Id: Ifcd5e8dbbe683dc99bb900a5870a9ba374fbd5d4