backends/x11: Use backend-side error traps for input configuration
While it's obviously good to trap possible errors from X calls, we are mixing the Clutter error trap with the MetaX11Display one for these calls.
This may result in situations where a X call within a Clutter error trap fails, but it's actually handled in these sections using the MetaX11Display error trap. This one will consider the serial out of the "handled" parts and raise an error.
It is better to stay consistent here, and use the same error traps than the rest of the X11 backend.
Closes: #2796 (closed)