[MISC] Always import version library first in the vllm package (#12979)

Signed-off-by: Lu Fang <lufang@fb.com>

vllm/__init__.py

 # SPDX-License-Identifier: Apache-2.0
 """vLLM: a high-throughput and memory-efficient inference engine for LLMs"""
+# The version.py should be independent library, and we always import the
+# version library first.  Such assumption is critical for some customization.
+from .version import __version__, __version_tuple__  # isort:skip
+
 import os
 
 import torch
@@ -19,8 +23,6 @@ from vllm.outputs import (ClassificationOutput, ClassificationRequestOutput,
 from vllm.pooling_params import PoolingParams
 from vllm.sampling_params import SamplingParams
 
-from .version import __version__, __version_tuple__
-
 # set some common config/environment variables that should be set
 # for all processes created by vllm and all processes
 # that interact with vllm workers.