title_bar: Remove dependency on command_palette (#21006)

This PR removes the `title_bar` crate's dependency on the
`command_palette`.

The `command_palette::Toggle` action now resides at
`zed_actions::command_palette::Toggle`.

Release Notes:

- N/A

crates/zed_actions/src/lib.rs

@@ -44,6 +44,12 @@ actions!(
     ]
 );
 
+pub mod command_palette {
+    use gpui::actions;
+
+    actions!(command_palette, [Toggle]);
+}
+
 #[derive(Clone, Default, Deserialize, PartialEq)]
 pub struct InlineAssist {
     pub prompt: Option<String>,