[rustdoc] Display unsafe attrs with edition 2024 `unsafe()` wrappers.
Use Rust 2024 edition representation for unsafe attributes in rustdoc HTML:
- `#[no_mangle]` -> `#[unsafe(no_mangle)]`
- `#[export_name = "foo"]` -> `#[unsafe(export_name = "foo")]`
- `#[link_section = ".text"]` -> `#[unsafe(link_section = ".text")]`
The 2024 edition representation is used regardless of the crate's own edition. This ensures that Rustaceans don't have to learn the rules of an outdated edition (e.g. that `unsafe()` wasn't always necessary) in order to understand a crate's documentation.
After some looking through the `T-rustdoc` issues, I was not able to find an existing issue for this. Apologies if I missed it.
r? ``````@aDotInTheVoid``````
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