Rollup of 4 pull requests
Successful merges:
- #124520 (Document that `create_dir_all` calls `mkdir`/`CreateDirW` multiple times)
- #124724 (Prefer lower vtable candidates in select in new solver)
- #124771 (Don't consider candidates with no failing where clauses when refining obligation causes in new solver)
- #124808 (Use `super_fold` in `RegionsToStatic` visitor)
r? `@ghost`
`@rustbot` modify labels: rollup