Defined a more generic way to let services "opt-out" from certain user types.

SystemService now defines a isSupported(UserInfo), which is used by SystemServiceManager to
skip the service for the unsupported types.

Also added a new argument to SystemService.onSwitch() to indicate which user is
being switched from.

Finally, also fixed VoiceInteractionManagerService so it doesn't start for headless user 0.

Test: manual verification
Test: atest CtsVoiceInteractionTestCases CtsAssistTestCases # on automotive and walleye

Bug: 133242016
Bug: 137878080

Change-Id: Ife4bd875f412f85cccf9c9fd03115abd238d7eab