Split EventBuilders.h

The `NotifyArgs.h` header is only available within inputflinger.
Therefore, the builders that rely on NotifyArgs need to be defined
in inputflinger, while MotionEvent-related builders can be defined
in libinput (so they can be used in libinput tests).

Test: `atest surfaceflinger_tests` passes.

Bug: 268245099

Change-Id: I9c9013d3fb8799bba0fa93a0d7dafd3b6b56a583