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/collab_ui/src/collab_panel/channel_modal.rs

@@ -408,11 +408,14 @@ impl PickerDelegate for ChannelModalDelegate {
                             .when(is_me, |el| el.child(Label::new("You").color(Color::Muted)))
                             .children(
                                 if let (Some((menu, _)), true) = (&self.context_menu, selected) {
-                                    Some(deferred(
-                                        anchored()
-                                            .anchor(gpui::AnchorCorner::TopRight)
-                                            .child(menu.clone()),
-                                    ))
+                                    Some(
+                                        deferred(
+                                            anchored()
+                                                .anchor(gpui::AnchorCorner::TopRight)
+                                                .child(menu.clone()),
+                                        )
+                                        .with_priority(1),
+                                    )
                                 } else {
                                     None
                                 },