Add sticky keys input filter

DD: go/pk_accessibility
'Sticky keys' is an accessibility feature that assists users
who have physical disabilities or help users reduce repetitive
strain injury. It serializes keystrokes instead of pressing
multiple keys at a time, allowing the user to press and
release a modifier key, such as Shift, Ctrl, Alt, or any other
modifier key, and have it remain active until any other key
is pressed.

Bug: 294546335
Test: TEST=libinputflinger_rs_test; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: Id26ed4a949e929cb6af8b9ecf1cd95c48fe20486