Deprecate runtime component loader

Author: T4rk1n

dash/development/component_loader.py

@@ -1,6 +1,7 @@
 import collections
 import json
 import os
+import warnings
 
 from ._py_components_generation import (
     generate_class_file,
@@ -35,6 +36,14 @@ def load_components(metadata_path, namespace="default_namespace"):
     `type`, `valid_kwargs`, and `setup`.
     """
 
+    warnings.warn(
+        DeprecationWarning(
+            "Dynamic components loading has been deprecated and will be removed"
+            " in dash 3.0.\n"
+            f"Update {namespace} to generate components with dash-generate-components"
+        )
+    )
+
     # Register the component lib for index include.
     ComponentRegistry.registry.add(namespace)
     components = []