[Misc] Add SPDX-License-Identifier headers to python source files (#12628)

- **Add SPDX license headers to python source files**
- **Check for SPDX headers using pre-commit**

commit 9d7ef44c3cfb72ca4c32e1c677d99259d10d4745
Author: Russell Bryant <rbryant@redhat.com>
Date:   Fri Jan 31 14:18:24 2025 -0500

    Add SPDX license headers to python source files
    
This commit adds SPDX license headers to python source files as
recommended to
the project by the Linux Foundation. These headers provide a concise way
that is
both human and machine readable for communicating license information
for each
source file. It helps avoid any ambiguity about the license of the code
and can
    also be easily used by tools to help manage license compliance.
    
The Linux Foundation runs license scans against the codebase to help
ensure
    we are in compliance with the licenses of the code we use, including
dependencies. Having these headers in place helps that tool do its job.
    
    More information can be found on ...

tests/engine/test_multiproc_workers.py

+# SPDX-License-Identifier: Apache-2.0
+
 import asyncio
 from concurrent.futures import ThreadPoolExecutor
 from functools import partial

tests/engine/test_short_mm_context.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from ..conftest import IMAGE_ASSETS

tests/engine/test_skip_tokenizer_init.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm.entrypoints.llm import LLM

tests/engine/test_stop_reason.py

+# SPDX-License-Identifier: Apache-2.0
 """Test the different finish_reason="stop" situations during generation:
     1. One of the provided stop strings
     2. One of the provided stop tokens

tests/engine/test_stop_strings.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import Any, List, Optional
 
 import pytest

tests/entrypoints/conftest.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 

tests/entrypoints/llm/test_accuracy.py

+# SPDX-License-Identifier: Apache-2.0
 """
 This file test accuracy of the vLLM server via LMEval.
 It uses local-completions, which interacts with vLLM

tests/entrypoints/llm/test_chat.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import List
 
 import pytest

tests/entrypoints/llm/test_collective_rpc.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm import LLM

tests/entrypoints/llm/test_encode.py

+# SPDX-License-Identifier: Apache-2.0
+
 import weakref
 from typing import List
 

tests/entrypoints/llm/test_generate.py

+# SPDX-License-Identifier: Apache-2.0
+
 import weakref
 from typing import List
 

tests/entrypoints/llm/test_generate_multiple_loras.py

+# SPDX-License-Identifier: Apache-2.0
+
 import weakref
 
 import pytest

tests/entrypoints/llm/test_gpu_utilization.py

+# SPDX-License-Identifier: Apache-2.0
+
 from vllm import LLM, SamplingParams
 
 

tests/entrypoints/llm/test_guided_generate.py

+# SPDX-License-Identifier: Apache-2.0
+
 import json
 import re
 import weakref

tests/entrypoints/llm/test_init.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm import LLM

tests/entrypoints/llm/test_lazy_outlines.py

+# SPDX-License-Identifier: Apache-2.0
+
 import sys
 from contextlib import nullcontext
 

tests/entrypoints/llm/test_prompt_validation.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm import LLM

tests/entrypoints/offline_mode/test_offline_mode.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests for HF_HUB_OFFLINE mode"""
 import importlib
 import sys

tests/entrypoints/openai/reasoning_parsers/test_deepseekr1_reasoning_parser.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import List
 
 import pytest

tests/entrypoints/openai/reasoning_parsers/utils.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import List, Optional, Tuple, Union
 
 from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,