Reland: Change input injection security model This reverts commit 861faa0811967a732a127568d9a306cb1565bdd8. Changes from revert: - Don't inject events from the shell uid in CTS tests Bug: 207667844 Bug: 194952792 Test: atest WindowFocusTests WindowInsetsControllerTests Test: TBD Change-Id: I84fa3b8cf630422ead0f4e5944f85c8e461c7f29 Merged-In: I84fa3b8cf630422ead0f4e5944f85c8e461c7f29