Change `AttrArgs::Eq` to a struct variant Cleanups for simplifying https://github.com/rust-lang/rust/pull/131808 Basically changes `AttrArgs::Eq` to a struct variant and then avoids several matches on `AttrArgsEq` in favor of methods on it. This will make future refactorings simpler, as they can either keep methods or switch to field accesses without having to restructure code