Initial check-in of in-memory prefab creation helpers for Dynamic Vegetation tests

Signed-off-by: jckand-amzn <jckand@amazon.com>

AutomatedTesting/Gem/PythonTests/EditorPythonTestTools/editor_python_test_tools/editor_entity_utils.py

@@ -132,6 +132,7 @@ class EditorEntity:
 
     def __init__(self, id: azlmbr.entity.EntityId):
         self.id: azlmbr.entity.EntityId = id
+        self.components: List[EditorComponent] = []
 
     # Creation functions
     @classmethod
@@ -258,6 +259,7 @@ class EditorEntity:
         :return: Component object of newly added component.
         """
         component = self.add_components([component_name])[0]
+        self.components.append(component)
         return component
 
     def add_components(self, component_names: list) -> List[EditorComponent]:
@@ -279,7 +281,7 @@ class EditorEntity:
             ), f"Failure: Could not add component: '{new_comp.get_component_name()}' to entity: '{self.get_name()}'"
             new_comp.id = add_component_outcome.GetValue()[0]
             components.append(new_comp)
-
+            self.components.append(new_comp)
         return components
 
     def get_components_of_type(self, component_names: list) -> List[EditorComponent]: