WIP: Switch to wlr-gamma-control protocol

The code is obviously not ready by any aesthetic standards, but it should already work. However, I couldn't get it to work via Night Light locally - in fact, the current code doesn't work for me either, nor does Mutter, so there's probably something else wrong with my setup (which isn't surprising with my patchwork GNOME installation).

Posting it now as it is since I want to do other stuff before I go into debugging what's broken on my machine.

Related: #62