Initial git panel refinements (#21912)

- Wire up settings
- Update static Panel impl
- Tidy up renders

Release Notes:

- N/A

crates/zed/src/main.rs

@@ -463,6 +463,7 @@ fn main() {
         call::init(app_state.client.clone(), app_state.user_store.clone(), cx);
         notifications::init(app_state.client.clone(), app_state.user_store.clone(), cx);
         collab_ui::init(&app_state, cx);
+        git_ui::init(cx);
         vcs_menu::init(cx);
         feedback::init(cx);
         markdown_preview::init(cx);

crates/zed/src/zed.rs

@@ -3477,6 +3477,7 @@ mod tests {
             language::init(cx);
             editor::init(cx);
             collab_ui::init(&app_state, cx);
+            git_ui::init(cx);
             project_panel::init((), cx);
             outline_panel::init((), cx);
             terminal_view::init(cx);