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/editor/src/element.rs

@@ -1812,6 +1812,7 @@ impl EditorElement {
                 .anchor(AnchorCorner::TopLeft)
                 .snap_to_window(),
         )
+        .with_priority(1)
         .into_any();
 
         element.layout(gpui::Point::default(), AvailableSpace::min_size(), cx);