Add verifyInputEvent api to InputDispatcher

Now InputDispatcher will be able to check whether a certain InputEvent
is legitimate.
Use the 'verifyInputEvent' api to determine if a given 'InputEvent'
actually came from InputDispatcher.

Bug: 134977432
Test: atest VerifiedKeyEventTest VerifiedMotionEventTest libinput_tests
inputflinger_tests
Change-Id: I8e7fa9bfa3c14b0b0d949fb5e28b43ff7583398f