Added draft of DataGridColumnsManager that uses Search and Dropdown

src/myfasthtml/core/instances.py

@@ -117,7 +117,7 @@ class BaseInstance:
       return _id
     
     if _id.startswith("-") and parent is not None:
-      return f"{parent.get_prefix()}{_id}"
+      return f"{parent.get_id()}{_id}"
     
     return _id