pane: Add settings to hide the tab bar buttons (#23752)

This PR adds the `show_tab_bar_buttons` under `tab_bar` that allows
hiding the "New", "Split Pane", and "Zoom" buttons to the left of the
pane tab bar.

Release Notes:

- Added a new `show_tab_bar_buttons` setting, under `tab_bar`, that
enables hiding the pane tab bar buttons.

crates/workspace/src/workspace_settings.rs

@@ -147,6 +147,7 @@ pub struct WorkspaceSettingsContent {
 pub struct TabBarSettings {
     pub show: bool,
     pub show_nav_history_buttons: bool,
+    pub show_tab_bar_buttons: bool,
 }
 
 #[derive(Clone, Default, Serialize, Deserialize, JsonSchema)]
@@ -159,6 +160,10 @@ pub struct TabBarSettingsContent {
     ///
     /// Default: true
     pub show_nav_history_buttons: Option<bool>,
+    /// Whether or not to show the tab bar buttons.
+    ///
+    /// Default: true
+    pub show_tab_bar_buttons: Option<bool>,
 }
 
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]