Rollup merge of #82798 - jyn514:rustdoc-group, r=Manishearth,GuillaumeGomez

Rollup merge of #82798 - jyn514:rustdoc-group, r=Manishearth,GuillaumeGomez

Rename `rustdoc` to `rustdoc::all`

When rustdoc lints were changed to be tool lints, the `rustdoc` group was removed, leading to spurious warnings like

```
warning: unknown lint: `rustdoc`
```

The lint group still worked when rustdoc ran, since rustdoc added the group itself.

This renames the group to `rustdoc::all` for consistency with `clippy::all` and the rest of the rustdoc lints.

Follow-up to #80527.
r? ``@Manishearth``