Ignore touchpad contacts that are marked as palms

Some touchpads detect palms in their firmware but continue to report
them, just marking them as palms (e.g. with MT_TOOL_PALM). Since the
Gestures library has no mechanism for marking incoming touches as
pre-detected palms, for now just completely ignore palms reported by the
touchpad.

Bug: 270041770
Test: atest inputflinger_tests:HardwareStateConverterTest
Test: limited manual testing
Change-Id: I7d898889d4bf4e8068194d22150c02a69b59c435