Add configuration for disabling stylus button motion events

This adds an option for disabling stylus buttons from being reported as
part of a motion gesture. When disabled, all reported motion events'
button state will not include any stylus buttons. Key events are
unaffected.

Bug: 263256832
Test: atest inputflinger_tests
Change-Id: If9ac98c77e980e6b45cfc012ed04b5541e350ebc