Add support for category comments in Nix option collection

The nix module now parses `/* */` comments as categories and associates
them with subsequent options. The output format has been updated to
include the category prefix before the option path. The internal state
is maintained during traversal to ensure correct category propagation
through nested structures.

src/main.rs

@@ -17,8 +17,8 @@ fn main() {
         eprintln!();
     }
 
-    let options: Vec<(String, bool)> = nix::collect_nix_options_with_path(&ast.syntax(), "");
-    for (path, value) in options {
-        println!("{} = {};", path, value);
+    let options: Vec<(String, String, bool)> = nix::collect_nix_options(&ast.syntax());
+    for (category, path, value) in options {
+        println!("{}: {} = {};", category, path, value);
     }
 }