title_bar: Remove dependency on theme_selector (#21009)

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

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

Release Notes:

- N/A

crates/zed_actions/src/lib.rs

@@ -50,6 +50,19 @@ pub mod command_palette {
     actions!(command_palette, [Toggle]);
 }
 
+pub mod theme_selector {
+    use gpui::impl_actions;
+    use serde::Deserialize;
+
+    #[derive(PartialEq, Clone, Default, Debug, Deserialize)]
+    pub struct Toggle {
+        /// A list of theme names to filter the theme selector down to.
+        pub themes_filter: Option<Vec<String>>,
+    }
+
+    impl_actions!(theme_selector, [Toggle]);
+}
+
 #[derive(Clone, Default, Deserialize, PartialEq)]
 pub struct InlineAssist {
     pub prompt: Option<String>,