Rollup merge of #140795 - mu001999-contrib:sugg-stable-import-first, r=petrochenkov

Prefer to suggest stable candidates rather than unstable ones

Fixes #140240

The logic is to replace unstable suggestions if we meet a new stable one, and do nothing if any other situation. In old logic, we just use the first candidate we meet as the suggestion for the same items.

E.g., `std::range::legacy::Range` vs `std::ops::Range`, `legacy` in the former is unstable, we prefer to suggest use the latter.

Author: fmease