xwayland hardcoded screen size limits to 8192x8192

Currently xwayland hardcodes limits screensize limits to 8192x8192 as seen here

This doesn't work well when something like xrandr reads the config with three 4k displays connected. On X with a Radeon it gets Screen 0: minimum 320 x 200, current 11520 x 2160, maximum 16384 x 16384 Theoretically on Nouveau/Nvidia/Intel the maximums will also end up going to 16k or 32k depending.

Would be nice to have xwayland query the real limits and pass them through without hardcoding them.