Reconstify `Add` r? project-const-traits I'm not happy with the ui test changes (or failures because I did not bless them and include the diffs in this PR). There is at least some bugs I need to look and try fix: 1. A third duplicated diagnostic when a consumer crate that does not have `effects` enabled has a trait selection error for an upstream const_trait trait. See tests/ui/ufcs/ufcs-qpath-self-mismatch.rs. 2. For some reason, making `Add` a const trait would stop us from suggesting `T: Add` when we try to add two `T`s without that bound. See tests/ui/suggestions/issue-97677.rs