Auto merge of #125284 - compiler-errors:uplift-misc, r=lcnr

Uplift `RegionVid`, `TermKind` to `rustc_type_ir`, and `EagerResolver` to `rustc_next_trait_solver`

- Uplift `RegionVid`. This was complicated due to the fact that we implement `polonius_engine::Atom` for `RegionVid` -- but I just separated that into `PoloniusRegionVid`, and added `From`/`Into` impls so it can be defined in `rustc_borrowck` separately. Coherence 😵
- Change `InferCtxtLike` to expose `opportunistically_resolve_{ty,ct,lt,int,float}_var` so that we can uplift `EagerResolver` for use in the canonicalization methods.
- Uplift `TermKind` much like `GenericArgKind`

All of this is miscellaneous dependencies for making more `EvalCtxt` methods generic.

Author: bors