Create an empty AccessibilityService APK for AccessibilityMenu.

AccessibilityMenu is moving from the Android Accessibility Suite and
into being a preinstalled APK in the system.

This change creates an empty no-op service that will be fleshed out in
later changes to include the full UI and functionality of
AccessibilityMenu.

Bug: 261252772
Test: build and install APK, enable empty service
Change-Id: I34275fa31a6d99dac13b4715a2f1a95e437004b3