A snippet is assigned a capability, which is then transferred to the
pipeline it gets added to. Managers of pipelines can then check whether
a pipeline it got handed whether it has a certain capability, and if
not, handle the situation where it is not.

The intention is to allow Clutter to tag color state transformation
snippets with a capability, allowing generic paint nodes to handle color
transformations when needed.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3433>