Add ChromeOS palm rejection model

This model will be used to block palm presses. It takes in a stream of
evdev events, and reports back the pointers which should be considered
palm.

Bug: 198472780
Test: atest libpalmrejection_test inputflinger_tests
Test: "adb shell device_config put input_native_boot
palm_rejection_enabled 0" and make sure that "adb shell dumpsys input"
shows that there aren't any palm rejectors inside
UnwantedInteractionBlocker

Change-Id: If979d335af29cf5e93b26336fea56a3a895cc562