Fixes Toast.show() for visible background users.

When its caller is a visible background user using a non-ui context
(like the application context), the Toast must be displayed in the
display the user was started visible on.

Test: atest --user-type secondary_user_on_secondary_display android.widget.cts.ToastTest#testShow_whenTextToast,testShow_appContext_whenTextToast

Test: atest android.widget.cts.ToastTest#testShow_whenTextToast,testShow_appContext_whenTextToast # to make sure the "normal" case still works

Test: atest NotificationManagerServiceTest

Fixes: 273314058
Bug: 272376728

Change-Id: I0a28d20462900eb0437781ab26d520be824014d1