Keycode logging logic for KeyboardSystemsEventReported atom

Implement logging logic for keyboard shortcuts (for the
KeyboardSystemsEventReported atom). The logging is done on a handler,
which logs the atoms on a separate thread.  Here, we log the atom for
KEYCODE_HOME.
The rest of the keycodes will be logged after a refactoring.

Bug: 280423320
Test: TBD
Change-Id: I950e77c2a6e734be28cc174b6be537fb308b283b