Basic side-by-side diff implementation (#43586)

Release Notes:

- N/A

---------

Co-authored-by: cameron <cameron.studdstreet@gmail.com>
Co-authored-by: Cameron <cameron@zed.dev>

crates/git_ui/src/commit_view.rs

@@ -513,7 +513,7 @@ impl Item for CommitView {
         }
     }
 
-    fn as_searchable(&self, _: &Entity<Self>) -> Option<Box<dyn SearchableItemHandle>> {
+    fn as_searchable(&self, _: &Entity<Self>, _: &App) -> Option<Box<dyn SearchableItemHandle>> {
         Some(Box::new(self.editor.clone()))
     }