Rollup merge of #133221 - Urgau:check-cfg-macro-diag, r=jieyouxu

Add external macros specific diagnostics for check-cfg

This PR adds specific check-cfg diagnostics for unexpected cfg in external macros.

As well as hiding the some of the Cargo specific help/suggestions as they distraction for external macros and are generally not the right solution.

Follow-up to #132577

`@rustbot` label +L-unexpected_cfgs
r? compiler

Author: matthiaskrgr