WIP: Make PickerDelegate a fully owned object instead of a view

This avoids issues with the parent view being on the stack when we want to
interact with the delegate from the picker. Still have several picker usages
to convert.

crates/theme_selector/src/theme_selector.rs

@@ -156,7 +156,7 @@ impl PickerDelegate for ThemeSelector {
         cx.emit(Event::Dismissed);
     }
 
-    fn dismiss(&mut self, cx: &mut ViewContext<Self>) {
+    fn dismissed(&mut self, cx: &mut ViewContext<Self>) {
         if !self.selection_completed {
             Self::set_theme(self.original_theme.clone(), cx);
             self.selection_completed = true;