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
3 files changed