rustdoc: render generic params & where-clauses of cross-crate assoc tys in impls
We used to only ever render generic parameters & where-clauses of cross-crate associated types when the item was located inside of a trait and we used to just drop them when it was inside of an impl block (trait or inherent).
Fixes#112904.
`@rustbot` label A-cross-crate-reexports
rustdoc: simplify DOM for `.item-table`
This switches from using `<div>` to the more semantic `<ul>`, and using class names that rhyme with the classes the search results table uses.
Since these elements now use `white-space: pre-wrap` since
784665d4ce, it's fine to use newlines
for formatting, which is smaller and a bit less complicated.
This class originated in the very first commit of `rustdoc_ng`, and was used
to add a color border around the item decl based on its kind.
4fd061c426/src/rustdoc_ng/html/static/main.css (L102-L106)
The item decl no longer has a border, and there aren't any
kind-specific styles in modern rustdoc's rendering of this UI item.
Most of this commit is updating test cases so that they use `item-decl` to
find the `<pre>` tag instead of relying on the fact that the class name
had `rust {kind}` in it while other `<pre>` tags only had class `rust`.
