Add ANR Subreason Test

This change adds a test that verifies the ANR subreason is populated in
the description of the ApplicationExitInfo object when the exit reason
is ANR.

Bug: 295599954
Test: atest CtsAppExitTestCases:ActivityManagerAppExitInfoTest
Flag: android.app.include_anr_subreason
Change-Id: Id3b88679f8dc8f1f18bf62feb0e9389ee7d0912e