Fix a few relative paths in rustc doc
## Changes
- Don't inline the doc for re-exporting some structs that have relative paths in doc.
## Context
See #124028.
- Most of the relative links in rustdoc are there because of circular import (so syntax like `[MyType]: rustc_foo::bar` is difficult to achieve when we cannot import `rustc_xxx` due to circular import)
- Here, I disable new links for re-exports. I think it's fine for re-exported items in `hir::*`.
- There is a few more relative links in other `rustc` crates, however they are not addressed in this PR, as they are not re-exported and/so the relative paths are working.
Closes#124028.
r? `@fmease`
Let me know if I miss anything or there's any other way to address this issue.
6d41be2700