a11y: Remove VoiceAccessShortcutController from PhoneWindowManager

With key gesture handler APIs, we can handle shortcuts in A11y
directly, this can allow components to react appropriately.
e.g. Use displayId passed in key gesture event to show UI on
correct display instead of routing that information from PWM to
A11y service.

Attaching original commit that adds voice access shortcut
(I116ac81f76198122b7ab4dce370197781386d06b) for completeness check.

Change-Id: I0f2a1c938c60772bbba19c3112c2d46cad26fc2f
Bug: 413279228
Test: atest AccessibilityManagerServiceTest
Flag: EXEMPT refactor