Also duplicate `#[expect]` attribute in `#[derive]`-ed code
This PR updates our derive logic to also duplicate any `#[expect]` attribute in the `#[derive]`-ed code, as we already do for all the other lint attribute (`#[allow]`, `#[warn]`, `#[deny]`, ...).
The original and duplicated attribute share the same attribute id, which due to the way [`check_expectations`](56aaf58ec0/compiler/rustc_lint/src/expect.rs (L28-L46)) is implemented makes the expectation fulfilled if the lint is either trigger in the original code or the derived code.
This was discussed by T-lang in https://github.com/rust-lang/rust/issues/150553#issuecomment-3780810363.
cc @rust-lang/lang-ops (in case you want to do an FCP)
Fixesrust-lang/rust#150553
fced23053c