Tracking Issue for rustc internal debug printing of infer var universes

[BoxyUwU]

#112984 introduced a way for rustc contributors to debug output the universes of ty/const/region vars. This comment lists a variety of things that should be followed up on. Particularly:

• Introduce derive(DebugWithInfcx)
• Do something about the way that type/consts store universes of infer vars differently than regions which makes debug output worse
• DebugWithInfcx and InferCtxtLike should have documentation stating what they are for and why they exist in the form they do (a lot of this can likely be taken from the PR description)

cc @compiler-errors

[BoxyUwU]

We no longer are attempting to support this as it is a complete mess :3