Rollup merge of #72710 - jsgf:unused-deps-test, r=jsgf
Rollup merge of #72710 - jsgf:unused-deps-test, r=jsgf

Add test to make sure -Wunused-crate-dependencies works with tests

Make sure code in `#[test]` blocks counts as a use of a crate.

graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust