InputDispatcher: Add hit test method isPointerInWindow

Before an app can successfully change the pointer icon, we want to
determine whether its windows are actually receiving the pointer.

To do this, we need to be able to do a hit test for a pointer in a
window, so we add a hit test method to InputDispatcher.

Bug: 293587049
Test: atest inputflinger_tests
Change-Id: I8ff103052f8ba58e411b3456f189eab020d49ef1