Auto merge of #125443 - nnethercote:rustfmt-use-decls, r=lcnr,cuviper,GuillaumeGomez

rustfmt `use` declarations

This PR implements rust-lang/compiler-team#750, which changes how `use` declarations are formatted by adding these options to `rustfmt.toml`:
```
group_imports = "StdExternalCrate"
imports_granularity = "Module"
```

r? `@ghost`

Author: bors

compiler/rustc_ast/src/util/comments.rs

@@ -1,6 +1,7 @@
-use crate::token::CommentKind;
 use rustc_span::{BytePos, Symbol};
 
+use crate::token::CommentKind;
+
 #[cfg(test)]
 mod tests;
 

compiler/rustc_ast/src/util/comments/tests.rs

@@ -1,6 +1,7 @@
-use super::*;
 use rustc_span::create_default_session_globals_then;
 
+use super::*;
+
 #[test]
 fn test_block_doc_comment_1() {
     create_default_session_globals_then(|| {