Use mmengine registry and fix the LoadAnnotations not in registry

mmcv/transforms/builder.py

 # Copyright (c) OpenMMLab. All rights reserved.
-from ..utils.registry import Registry
-
-TRANSFORMS = Registry('transform')
+from mmengine.registry import TRANSFORMS

mmcv/transforms/loading.py

@@ -84,6 +84,7 @@ class LoadImageFromFile(BaseTransform):
         return repr_str
 
 
+@TRANSFORMS.register_module()
 class LoadAnnotations(BaseTransform):
     """Load and process the ``instances`` and ``seg_map`` annotation provided
     by dataset.