Revert "Revert "Defer FGS notifications from legacy apps by default""

This reverts commit 33de1a2d.

Re-establishing this behavior now that the unit test failure has been
isolated and fixed.

Reason for revert: test/app fix
Bug: 175764941
Bug: 176849372
Test: atest TraceurUiTests:com.android.traceur.uitest.TraceurAppTests#testSuccessfulTracing
Test: ApiDemos

Change-Id: I3fa20e1a37eade5ee8de6f7e10d7eed851d877d1