rustdoc: Cleanup `clean` part 1
Split out from #88379.
These commits are completely independent of each other, and each is a fairly
small change (the last few are new commits; they are not from #88379):
- Remove unnecessary `Cache.*_did` fields
- rustdoc: Get symbol for `TyParam` directly
- Create a valid `Res` in `external_path()`
- Remove unused `hir_id` parameter from `resolve_type`
- Fix redundant arguments in `external_path()`
- Remove unnecessary `is_trait` argument
- rustdoc: Cleanup a pattern match in `external_generic_args()`
r? ``@jyn514``
Change more x64 size checks to not apply to x32.
Commit 95e096d6 changed a bunch of size checks already, but more have
been added, so this fixes the new ones the same way: the various size
checks that are conditional on target_arch = "x86_64" were not intended
to apply to x86_64-unknown-linux-gnux32, so add
target_pointer_width = "64" to the conditions.
Fix table in docblocks
"Overwrite" of #88702.
Instead of adding a z-index to the sidebar (which only hides the issue, doesn't fix it), I wrap `<table>` elements inside a `<div>` and limit all chidren of `.docblock` elements' width to prevent having the scrollbar on the whole doc block.

Thanks `@nbdd0121` for `overflow-x: auto;`. ;)
r? `@notriddle`
Avoid invoking the hir_crate query to traverse the HIR
Walking the HIR tree is done using the `hir_crate` query. However, this is unnecessary, since `hir_owner(CRATE_DEF_ID)` provides the same information. Since depending on `hir_crate` forces dependents to always be executed, this leads to unnecessary work.
By splitting HIR and attributes visits, we can avoid an edge to `hir_crate` when trying to visit the HIR tree.
Commit 95e096d6 changed a bunch of size checks already, but more have
been added, so this fixes the new ones the same way: the various size
checks that are conditional on target_arch = "x86_64" were not intended
to apply to x86_64-unknown-linux-gnux32, so add
target_pointer_width = "64" to the conditions.
Display associated types of implementors
Fixes#86631.
Contrary to before, it doesn't display methods. I also had to "resurrect" the `auto-hide-trait-implementations` setting. :3
Only question at this point: should I move the `render_impl` boolean arguments into one struct? We're starting to have quite a lot of them...
cc `@cynecx`
r? `@camelid`
[rustdoc] Wrap code blocks in <code> tag
This PR modifies Rustdoc output so that fenced code snippets, items and whole file source codes are wrapped in `<pre><code>` instead of just `<pre>`. This should improve the semantic meaning of the generated content.
I'm not sure what to do about `render_attributes_in_pre` and `render_attributes_in_code`. These functions were clearly expected to be used for things inside `<pre>` or `<code>`, and since I added `<code>` in this PR, some of them will be used in a different context than before. However, it seems to me that even before they were not consistent. For example, `item_constant` used `render_attributes_in_code` for its attributes, however there was no `<code>` used for constants before this PR...
Should I create some `rustdoc-gui` tests? For example to check that all `<pre>` tags have a `<code>` child?
Fixes: https://github.com/rust-lang/rust/issues/88020
[rustdoc] Copy only item path to clipboard rather than full `use` statement.
The (somewhat) recent addition of the "copy item import to clipboard" button is extremely nice.
However, i tend to write my code with fully qualified paths wherever feasible and only resort to `use` statements as a refactoring pass. This makes the "copy to clipboard" workflow awkward to use, as i would be copy-pasting that as, say
```rust
impl use std::ops::Add; for MyType {
```
and then go back and remove the `use ` and `;`.
This PR removes the `use ;` decorations, making it much nicer to use for fully-qualified items. I argue, however, that this does not noticeably degrade experience for those who prefer to import items, since the hard part about those is getting the path right, and writing the `use ;` decoration can be done by hand with little effort.