Update KL and KCM usages for new optional outputs

We updated some APIs to return std::optional. Use those APIs here in the
jni code.

Per our docs for MotionEvent and KeyEvent, in the event of failure, we
should be returning -1 and KEYCODE_UNKNOWN, respectively, so update the
code to actually follow this spec.

Bug: 266400536
Test: m
Change-Id: I8e414b1ec104a6458b1bc45b220eb9eeef99df21