Auto merge of #118924 - Urgau:check-cfg-exclude-well-known-from-diag,…

… r=petrochenkov

Exclude well known names from showing a suggestion in check-cfg

This PR adds an exclusion for well known names from showing in suggestions of check-cfg/`unexpected_cfgs`.

Follow-up to rust-lang/rust#118213 and fixes rust-lang/rust#118213 (comment).

r? `@petrochenkov`