Call ActivityTaskManagerService's version of hasSystemAlertWindowPermission().

Which checks both AppOps and PackageManager for SYSTEM_ALERT_WINDOW
permission.

Bug: 182491885.
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java
Change-Id: I05c19e089bb2d5daa4c8819f009eca2aa0d44c2f