globalshortcutsregistry: treat SysReq as Alt+Print

For shortcut purposes, treat SysReq as Alt+Print.
This enables setting shortcuts like Alt+Print.

Known limitation: when using Mod(s)+Alt+Print as shortcut,
only works when Alt is released before Mod(s).
Also doesn't work in MultiKey shortcuts.

BUG: 386253


(cherry picked from commit a6bc3a92)