debugger: Add debug task picker to new session modal (#29702)

## Preview 

![image](https://github.com/user-attachments/assets/203a577f-3b38-4017-9571-de1234415162)


### TODO
- [x] Add scenario picker to new session modal
- [x] Make debugger start action open new session modal instead of task
modal
- [x] Fix `esc` not clearing the cancelling the new session modal while
it's in scenario or attach mode
- [x] Resolve debug scenario's correctly

Release Notes:

- N/A

crates/picker/src/picker.rs

@@ -588,7 +588,9 @@ impl<D: PickerDelegate> Picker<D> {
                 self.update_matches(query, window, cx);
             }
             editor::EditorEvent::Blurred => {
-                self.cancel(&menu::Cancel, window, cx);
+                if self.is_modal {
+                    self.cancel(&menu::Cancel, window, cx);
+                }
             }
             _ => {}
         }