setcap on kwin

[David Edmundson]

That was true, we need to research and see if it's still true.
Gnome have dropped their cap_sys_nice.

For setting nice we many options:
 - kwin_wayland_wrapper can be cap_sys_nice set it the nice a child
PID (needs verifying)
 - maybe the systemd cgroup settings for priority are as good/better
 - rtkit

EGL contexts Carlos from Mutter says in a related gnome MR:

"EGL_CONTEXT_PRIORITY_HIGH_IMG is already obtainable without
additional capabilities (at least in the i915 driver)"
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2284

There's also an open mesa MR to cache context prioirty perimissions at
the time the context is created, which might allow for dropping after
initial setup.