project panel: Add setting to disable auto opening project panel (#34752)

Release Notes:

- Add `project_panel.starts_open` to control opening project panel in
new projects.

crates/project_panel/src/project_panel.rs

@@ -5625,6 +5625,10 @@ impl Panel for ProjectPanel {
     }
 
     fn starts_open(&self, _: &Window, cx: &App) -> bool {
+        if !ProjectPanelSettings::get_global(cx).starts_open {
+            return false;
+        }
+
         let project = &self.project.read(cx);
         project.visible_worktrees(cx).any(|tree| {
             tree.read(cx)