[Enhancement] Format the log of `CheckpointLoader.load_checkpoint` (#685)

* Format log of

* Fix as comment

* Update mmengine/runner/checkpoint.py

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

mmengine/runner/checkpoint.py

@@ -236,15 +236,14 @@ class CheckpointLoader:
                 return cls._schemes[p]
 
     @classmethod
-    def load_checkpoint(cls, filename, map_location=None, logger=None):
+    def load_checkpoint(cls, filename, map_location=None, logger='current'):
         """load checkpoint through URL scheme path.
 
         Args:
             filename (str): checkpoint file name with given prefix
             map_location (str, optional): Same as :func:`torch.load`.
                 Default: None
-            logger (:mod:`logging.Logger`, optional): The logger for message.
-                Default: None
+            logger (str): The logger for message. Defaults to 'current'.
 
         Returns:
             dict or OrderedDict: The loaded checkpoint.
@@ -252,8 +251,10 @@ class CheckpointLoader:
 
         checkpoint_loader = cls._get_checkpoint_loader(filename)
         class_name = checkpoint_loader.__name__
-        print_log(f'{class_name[10:]} loads checkpoint from path: {filename}',
-                  logger)
+        print_log(
+            f'Loads checkpoint by {class_name[10:]} backend from path: '
+            f'{filename}',
+            logger=logger)
         return checkpoint_loader(filename, map_location)