Make close sidebar button work regardless of focus state (#52260)

Like https://github.com/zed-industries/zed/pull/52045, but for the
*close* button.

Release Notes:

- N/A

crates/sidebar/src/sidebar.rs

@@ -2916,7 +2916,11 @@ impl Sidebar {
                     .into_any_element()
             }))
             .on_click(|_, window, cx| {
-                window.dispatch_action(ToggleWorkspaceSidebar.boxed_clone(), cx);
+                if let Some(multi_workspace) = window.root::<MultiWorkspace>().flatten() {
+                    multi_workspace.update(cx, |multi_workspace, cx| {
+                        multi_workspace.close_sidebar(window, cx);
+                    });
+                }
             })
     }
 }

crates/workspace/src/multi_workspace.rs

@@ -278,7 +278,7 @@ impl MultiWorkspace {
         cx.notify();
     }
 
-    fn close_sidebar(&mut self, window: &mut Window, cx: &mut Context<Self>) {
+    pub fn close_sidebar(&mut self, window: &mut Window, cx: &mut Context<Self>) {
         self.sidebar_open = false;
         let has_notifications = self.sidebar_has_notifications(cx);
         let show_toggle = self.multi_workspace_enabled(cx);