CursorInputMapper: tidy up the tests

Mostly, use Each matchers for repetitive checks on NotifyMotionArgs, but
also use the aliases for AMOTION_EVENT_ACTION_* constants and use a
WithRelativeMotion matcher in one case where it had been missed.

Bug: 245989146
Test: atest frameworks/native/services/inputflinger/tests/CursorInputMapper_test.cpp
Flag: TEST_ONLY
Change-Id: I866b0f44a02530896e5ea5f3f9047e66346f9116