[Bugfix] Allow custom visualizer (open-mmlab#3455)

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## Motivation

Current Visualization Hook can only get instances of
`SegLocalVisualizer`. This makes impossible to use any other custom
implementation.

## Modification

This PR just allows to instantiate a different visualizer (following
mmdetection implementation):

https://github.com/open-mmlab/mmdetection/blob/main/mmdet/engine/hooks/visualization_hook.py#L58

Author: mmeendez8

mmseg/engine/hooks/visualization_hook.py

@@ -7,10 +7,10 @@
 import mmengine.fileio as fileio
 from mmengine.hooks import Hook
 from mmengine.runner import Runner
+from mmengine.visualization import Visualizer
 
 from mmseg.registry import HOOKS
 from mmseg.structures import SegDataSample
-from mmseg.visualization import SegLocalVisualizer
 
 
 @HOOKS.register_module()
@@ -42,8 +42,7 @@ def __init__(self,
                  show: bool = False,
                  wait_time: float = 0.,
                  backend_args: Optional[dict] = None):
-        self._visualizer: SegLocalVisualizer = \
-            SegLocalVisualizer.get_current_instance()
+        self._visualizer: Visualizer = Visualizer.get_current_instance()
         self.interval = interval
         self.show = show
         if self.show: