[FEATURE] Move IMGUI skin out of SpaceWarp

[jan-bures]

Feature Information

Feature description

SpaceWarp no longer depends on the IMGUI skin that it provides, and the skin itself is considered deprecated in code.

Solution proposal

In 2.0 we should move it outside of SpaceWarp into its own separate mod or at least a separate SpaceWarp 2.0 module plugin (e.g. SpaceWarp.LegacyUI) as part of the larger SW 2.0 refactor, which is supposed to remove support for deprecated features. That way, modders will still be able to use it if they really want to, but it will be discouraged.