[Misc] Refactor tokenizer interface (#29693)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/entrypoints/test_chat_utils.py

@@ -28,8 +28,8 @@ from vllm.multimodal.utils import (
     encode_image_base64,
     encode_video_base64,
 )
+from vllm.tokenizers import MistralTokenizer
 from vllm.transformers_utils.tokenizer import get_tokenizer
-from vllm.transformers_utils.tokenizers.mistral import MistralTokenizer
 
 from ..models.registry import HF_EXAMPLE_MODELS
 from ..utils import VLLM_PATH