Tidy vllm/config/__init__.py to only add classes and functions (#26405)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

tests/distributed/test_expert_parallel.py

@@ -6,7 +6,7 @@ from typing import Literal, NamedTuple, Optional
 
 import pytest
 
-from vllm.config import RunnerOption
+from vllm.config.model import RunnerOption
 from vllm.logger import init_logger
 
 from ..utils import compare_two_settings, create_new_process_for_each_test