Use consistent coordinate extraction code in dispatcher

Consolidate the code for extraction of the coordinates from MotionEntry.
This allows us to more easily change the behaviour in the future.

In this CL, there will be a behaviour change that we will now use mouse
cursor position for some of the location resolution instead of pointer.
This should be OK to do.

Bug: 250029068
Test: atest inputflinger_tests
Change-Id: I137c26f881ad993f7a7463c2c05674e48cf864f4