DO NOT MERGE: Verify KeyEvents in IME

Malicious app can inject fabricated InputEvents into IME's FD which can
do tinker with special shortcuts like switching IME.
With this CL, all KeyEvents with modifiers OR indicated sensitive by IME will be
verified before being dispatched to IME.

For any events that are replayed, verify timestamp.

Bug: 331730488
Test: atest CtsInputMethodTestCases InputMethodServiceTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:8d730cf69b864336fd492c88049efc937fac6b61)
Merged-In: I6589cc73839acb6b2c3f9256c664b5db7e1ade8a
Change-Id: I6589cc73839acb6b2c3f9256c664b5db7e1ade8a