New Autofill API: SaveCallback.onSuccess(IntentSender).

This overloaded method is useful for cases where the service needs to launch
an activity (for example, to unlock the user's vault), in which case it's
launched from the context of the activity being filled.

Test: atest CtsAutoFillServiceTestCases:SimpleSaveActivityTest#testSave_launchIntent
Test: atest CtsAutoFillServiceTestCases
Fixes: 69458616

Change-Id: I41bf5fd4954c38051e3275f2e8500a00dcf24724