New Autofill API:AutofillManager.getAutofillServiceComponentName()

Also minor fixes on isFieldClassificationEnabled() to make sure it's ignored
when not called by the service app and its calls are properly synchronized.

Test: atest CtsAutoFillServiceTestCases:LoginActivityTest#testGetAutofillServiceComponentName

Fixes: 70678279

Change-Id: I58ccb313d22c30af907f3da62f727f067240fa66