Rollup merge of #127333 - compiler-errors:infer_ctxt_like-again, r=lcnr

Split `SolverDelegate` back out from `InferCtxtLike`

This is because in order to uplift things like the `Generalizer` and other `TypeRelation`s, we want to be able to interface with `InferCtxtLike` (and `InferCtxt` as its implementation), rather that `SolverDelegate`, which only really exists as a hack to be able to define some downstream methods in `rustc_type_ir`.

r? lcnr

Author: compiler-errors