Add support for detecting tests in source files, and implement it for Rust (#11195)

Continuing work from #10873 

Release Notes:

- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/collab/src/tests/editor_tests.rs

@@ -667,7 +667,7 @@ async fn test_collaborating_with_code_actions(
     editor_b.update(cx_b, |editor, cx| {
         editor.toggle_code_actions(
             &ToggleCodeActions {
-                deployed_from_indicator: false,
+                deployed_from_indicator: None,
             },
             cx,
         );