[Misc] Move utils to avoid conflicts with stdlib, and move tests (#27169)

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

vllm/entrypoints/llm.py

@@ -76,7 +76,7 @@ from vllm.transformers_utils.tokenizer import (
 )
 from vllm.usage.usage_lib import UsageContext
 from vllm.utils import Counter, Device
-from vllm.utils.collections import as_iter, is_list_of
+from vllm.utils.collection_utils import as_iter, is_list_of
 from vllm.v1.engine import EngineCoreRequest
 from vllm.v1.engine.llm_engine import LLMEngine
 from vllm.v1.sample.logits_processor import LogitsProcessor