Auto merge of #100574 - Urgau:check-cfg-warn-cfg, r=petrochenkov

Add warning against unexpected --cfg with --check-cfg

This PR adds a warning when an unexpected `--cfg` is specified but not in the specified list of `--check-cfg`.

This is the follow-up PR I mentioned in https://github.com/rust-lang/rust/pull/99519.

r? `@petrochenkov`

compiler/rustc_lint/src/lib.rs

@@ -146,6 +146,7 @@ macro_rules! early_lint_passes {
                 IncompleteFeatures: IncompleteFeatures,
                 RedundantSemicolons: RedundantSemicolons,
                 UnusedDocComment: UnusedDocComment,
+                UnexpectedCfgs: UnexpectedCfgs,
             ]
         );
     };