Allow to reuse PickerPopoverMenu outside of the model selector (#31684)

LSP button preparation step: move out the component that will be used to
build the button's context menu.

Release Notes:

- N/A

crates/picker/src/picker.rs

@@ -1,3 +1,7 @@
+mod head;
+pub mod highlighted_match_with_paths;
+pub mod popover_menu;
+
 use anyhow::Result;
 use editor::{
     Editor,
@@ -20,9 +24,6 @@ use ui::{
 use util::ResultExt;
 use workspace::ModalView;
 
-mod head;
-pub mod highlighted_match_with_paths;
-
 enum ElementContainer {
     List(ListState),
     UniformList(UniformListScrollHandle),