rust: Improve highlighting within macros (zed-industries#37049)

This makes sure we do not apply the highlights for snake case
identifiers as well as paths for attributes too broadly to all types of
macros, which should make macros much more readable overall whilst
keeping the highlighting for the attribute items.

| Before | After |
| --- | --- |
| <img width="1414" height="958" alt="Bildschirmfoto 2025-08-28 um 00 37
58"
src="https://github.com/user-attachments/assets/1254b9a2-d07a-4be4-9b4f-555a7c640302"
/> | <img width="1414" height="958" alt="Bildschirmfoto 2025-08-28 um 00
37 38"
src="https://github.com/user-attachments/assets/5f6dd66c-5469-4f27-9f1d-0a6e6e8d8085"
/> |

Release Notes:

- rust: Improved highlighting within macros.

Author: MrSubidubi

crates/languages/src/rust/highlights.scm

@@ -195,12 +195,13 @@ operator: "/" @operator
 (attribute_item (attribute [
   (identifier) @attribute
   (scoped_identifier name: (identifier) @attribute)
+  (token_tree (identifier) @attribute (#match? @attribute "^[a-z\\d_]*$"))
+  (token_tree (identifier) @variable "::" (identifier) @type (#match? @type "^[A-Z]"))
 ]))
+
 (inner_attribute_item (attribute [
   (identifier) @attribute
   (scoped_identifier name: (identifier) @attribute)
+  (token_tree (identifier) @attribute (#match? @attribute "^[a-z\\d_]*$"))
+  (token_tree (identifier) @variable "::" (identifier) @type (#match? @type "^[A-Z]"))
 ]))
-; Match nested snake case identifiers in attribute items.
-(token_tree (identifier) @attribute (#match? @attribute "^[a-z\\d_]*$"))
-; Override the attribute match for paths in scoped type/enum identifiers.
-(token_tree (identifier) @variable "::" (identifier) @type (#match? @type "^[A-Z]"))