Draft: cursor: Refactor for server side

Hi Wayland team,

I work on a compositor and would like to see libwayland-cursor function a bit more like xkbcommon working both for server-side(compositors) and clients. Partially as it seems a little wasteful for every compositor backend to be re-implementing some of the common methods here. Along with just being a nice QOL thing for compositor developers allowing them skip refactoring libXcursors into their project.

My changes don't break the current API so clients currently using libwayland-cursor are unaware of any changes are should continue to work(I've tested foot, firefox, fuzzel, wofi, and a few others) and I've tested it with my compositor(and it's made my cursor shaping code so much simpler).

I am curious to hear the thoughts of people here if this is something that you would even be interested in merging(once I clean the code up more). Or if there are any suggestions or concerns about the way I've currently implemented it.

Thank you and Kind regards Cat