Auto merge of rust-lang#80300 - LeSeulArtichaut:80275-doc-inline, r=Manishearth

Emit errors/warns on some wrong uses of rustdoc attributes

This PR adds a few diagnostics:
- error if conflicting `#[doc(inline)]`/`#[doc(no_inline)]` are found
- introduce the `invalid_doc_attributes` lint (warn-by-default) which triggers:
  - if a crate-level attribute is used on a non-`crate` item
  - if `#[doc(inline)]`/`#[doc(no_inline)]` is used on a non-`use` item

The code could probably be improved but I wanted to get feedback first. Also, some of those changes could be considered breaking changes, so I don't know what the procedure would be? ~~And finally, for the warnings, they are currently hard warnings, maybe it would be better to introduce a lint?~~ (EDIT: introduced the `invalid_doc_attributes` lint)

Closes rust-lang#80275.
r? `@jyn514`

Author: bors

std/src/os/emscripten/raw.rs

@@ -22,7 +22,6 @@ pub type mode_t = u32;
 #[stable(feature = "pthread_t", since = "1.8.0")]
 pub type pthread_t = c_ulong;
 
-#[doc(inline)]
 #[stable(feature = "raw_ext", since = "1.1.0")]
 pub type blkcnt_t = u64;
 #[stable(feature = "raw_ext", since = "1.1.0")]