Fix panel drag leaking through overlay (#10035)

Closes #10017. While reworking the `overlay` element in #9911, I did not
realize that all overlay elements called `defer_draw` with a priority of
`1`.

/cc @as-cii 

Not including release notes, since it was only present in nightly.

Release Notes:

- N/A

crates/project_panel/src/project_panel.rs

@@ -1590,6 +1590,7 @@ impl Render for ProjectPanel {
                             .anchor(gpui::AnchorCorner::TopLeft)
                             .child(menu.clone()),
                     )
+                    .with_priority(1)
                 }))
         } else {
             v_flex()