Add `let_underscore_must_use` lint changelog: closes #4812 , added a new `let_underscore_must_use` lint, moved `is_must_use_ty` to utils, added `is_must_use_fn` util function
Add `let_underscore_must_use` lint changelog: closes #4812 , added a new `let_underscore_must_use` lint, moved `is_must_use_ty` to utils, added `is_must_use_fn` util function