Move token related functions to common (#10942)

### What problem does this PR solve?

As title

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

graphrag/general/extractor.py

@@ -38,7 +38,7 @@ from graphrag.utils import (
 )
 from rag.llm.chat_model import Base as CompletionLLM
 from rag.prompts.generator import message_fit_in
-from rag.utils import truncate
+from common.token_utils import truncate
 
 GRAPH_FIELD_SEP = "<SEP>"
 DEFAULT_ENTITY_TYPES = ["organization", "person", "geo", "event", "category"]