Convert prefab to temp spawnable assets (#6179)

* Convert prefab to temp in-memory spawnable assets

Signed-off-by: chiyenteng <82238204+chiyenteng@users.noreply.github.com>

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

@@ -58,7 +58,10 @@ def launch_and_validate_results(request, test_directory, editor, editor_script,
     if null_renderer:
         editor.args.extend(["-rhi=Null"])
     if enable_prefab_system:
-        editor.args.extend(["--regset=/Amazon/Preferences/EnablePrefabSystem=true"])
+        from os import path
+        editor.args.extend([
+            "--regset=/Amazon/Preferences/EnablePrefabSystem=true",
+            f"--regset-file={os.path.join(workspace.paths.engine_root(), 'Registry', 'prefab.test.setreg')}"])
     else:
         editor.args.extend(["--regset=/Amazon/Preferences/EnablePrefabSystem=false"])
 

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

@@ -39,7 +39,6 @@ def get_prefab_file_path(prefab_path):
         prefab_path = name + ".prefab"
     return prefab_path
 
-
 def get_all_entity_ids():
     return entity.SearchBus(bus.Broadcast, 'SearchEntities', entity.SearchFilter())