Introduce multi-cursor inline transformations (#13368)

https://github.com/zed-industries/zed/assets/482957/591def34-e5c8-4402-9c6b-372cbca720c3

Release Notes:

- N/A

---------

Co-authored-by: Richard Feldman <oss@rtfeldman.com>

crates/diagnostics/src/diagnostics.rs

@@ -137,7 +137,7 @@ impl ProjectDiagnosticsEditor {
                     this.summary = project.read(cx).diagnostic_summary(false, cx);
                     cx.emit(EditorEvent::TitleChanged);
 
-                    if this.editor.read(cx).is_focused(cx) || this.focus_handle.is_focused(cx) {
+                    if this.editor.focus_handle(cx).contains_focused(cx) || this.focus_handle.contains_focused(cx) {
                         log::debug!("diagnostics updated for server {language_server_id}, path {path:?}. recording change");
                     } else {
                         log::debug!("diagnostics updated for server {language_server_id}, path {path:?}. updating excerpts");