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Auto merge of #118841 - compiler-errors:always-copy, r=jackh726
Make most `rustc_type_ir` kinds `Copy` by default
1. There's no reason why `TyKind` and `ConstKind`/`ConstData` can't be `Copy`. This allows us to avoid needing a typed arena for the two types.
2. Simplify some impls into derives.
