[EXPERIMENTAL] rework overrides

[indietyp]

(This is based on feature/split-supports-std, therefore the diff is a bit messy)

This is an idea that I had that I'd love to get your opinion on. (Implements #87)

This completely reworks overrides and creates a module with optionally more fine-grained control. One can set the override for either ansi, xterm, or truecolor, and that value will be respected, introspection of supported (including overrides), and override status is supported.

^{(Once again: I completely understand if this is too drastic of a change, this is why I implemented most of the code, but documentation and tests are largely missing. Please let me know if this is something you agree with/what needs to be changed or if this is not appropriate for this kind of library)}