Rollup merge of #139184 - Urgau:crate-root-lint-levels, r=jieyouxu

Add unstable `--print=crate-root-lint-levels`

This PR implements `--print=crate-root-lint-levels` from MCP 833 https://github.com/rust-lang/compiler-team/issues/833.

Tracking issue: https://github.com/rust-lang/rust/issues/139180

Best reviewed commit by commit.