Cache `is_vision_available` result (#29280)

Cache `is_vision_available`

This check is used quite often during process in image models and can take up a serious amount of time compared to the other processing steps.

src/transformers/utils/import_utils.py

@@ -741,6 +741,7 @@ def is_tokenizers_available():
     return _tokenizers_available
 
 
+@lru_cache
 def is_vision_available():
     _pil_available = importlib.util.find_spec("PIL") is not None
     if _pil_available: