Rollup merge of #124320 - Urgau:print-check-cfg, r=petrochenkov

Add `--print=check-cfg` to get the expected configs

This PR adds a new `--print` variant `check-cfg` to get the expected configs.

Details and rational can be found on the MCP: rust-lang/compiler-team#743

``@rustbot`` label +F-check-cfg +S-waiting-on-MCP
r? ``@petrochenkov``

Author: jieyouxu