MotionEvent: add safe dumping method

This method should allow us to log more details of an event in case of
validation failures, without potential for infinite recursion in getter
methods.

Bug: 379368465
Test: add a test to MotionEventTest that calls
      getHistoricalRawPointerCoords with an invalid pointer index, and
      check the logs when run with `atest --host`
Flag: EXEMPT logs only
Change-Id: I9c7084cedbc7e6f6834cd1b401da04d07d22ce35