refactor(workflow-file): move core.file to core.workflow.file (#32252)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/memory/token_buffer_memory.py

@@ -4,7 +4,6 @@ from sqlalchemy import select
 from sqlalchemy.orm import sessionmaker
 
 from core.app.app_config.features.file_upload.manager import FileUploadConfigManager
-from core.file import file_manager
 from core.model_manager import ModelInstance
 from core.model_runtime.entities import (
     AssistantPromptMessage,
@@ -16,6 +15,7 @@ from core.model_runtime.entities import (
 )
 from core.model_runtime.entities.message_entities import PromptMessageContentUnionTypes
 from core.prompt.utils.extract_thread_messages import extract_thread_messages
+from core.workflow.file import file_manager
 from extensions.ext_database import db
 from factories import file_factory
 from models.model import AppMode, Conversation, Message, MessageFile