Deny ApplicationThread usage from Non-System

This is a followup to ag/35270160 which just logged the violations.
Since there were a few calls from root (uid 0) to several dump* methods (I assume triggered via adb) root is now also considered a valid caller.

Bug: 317346668
Test: atest ActivityThreadTest BackgroundActivityLaunchTest
Flag: android.security.check_application_thread_called_by_system
Change-Id: I8d930700f4cf42a4de5576b79149a522f77808e6