Rollup merge of #154886 - chenyukang:yukang-fix-cfg-sugg, r=JonathanBrouwer

Stabilize check-cfg suggestions for symbol

When I was working on rust-lang/rust#154794, I found a weird CI fail rust-lang/rust#154794 (comment), I finally found this caused by unstable cfg suggestions by using `FxHashSet`(from PR rust-lang/rust#154777). Because my PR by luck insert a new symbol, which makes the final diagnostic order changed.

It's a standalone issue, so it's better to fix in a separate PR.

Author: JonathanBrouwer