[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/spec_decode/e2e/test_ngram_correctness.py

+# SPDX-License-Identifier: Apache-2.0
 """This docstring details important information on the testing methodology.
 
 Most of the tests rely on "greedy equality", where we expect the output of

tests/spec_decode/e2e/test_seed.py

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

tests/spec_decode/test_batch_expansion.py

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

tests/spec_decode/test_dynamic_spec_decode.py

+# SPDX-License-Identifier: Apache-2.0
+
 from unittest.mock import MagicMock, patch
 
 import pytest

tests/spec_decode/test_metrics.py

+# SPDX-License-Identifier: Apache-2.0
+
 import math
 from unittest.mock import MagicMock
 

tests/spec_decode/test_multi_step_worker.py

+# SPDX-License-Identifier: Apache-2.0
+
 import random
 from typing import Dict, List
 from unittest.mock import MagicMock

tests/spec_decode/test_ngram_worker.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 
 from vllm.sequence import ExecuteModelRequest

tests/spec_decode/test_scorer.py

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

tests/spec_decode/test_spec_decode_worker.py

+# SPDX-License-Identifier: Apache-2.0
+
 import random
 from collections import defaultdict
 from types import SimpleNamespace

tests/spec_decode/test_utils.py

+# SPDX-License-Identifier: Apache-2.0
+
 from unittest.mock import MagicMock
 
 import pytest

tests/spec_decode/utils.py

+# SPDX-License-Identifier: Apache-2.0
+
 from itertools import count
 from typing import Callable, Dict, List, Optional
 from typing import Sequence as GenericSequence

tests/standalone_tests/lazy_torch_compile.py

+# SPDX-License-Identifier: Apache-2.0
+
 # Description: Test the lazy import module
 # The utility function cannot be placed in `vllm.utils`
 # this needs to be a standalone script

tests/tensorizer_loader/conftest.py

+# SPDX-License-Identifier: Apache-2.0
+
 import functools
 import gc
 from typing import Callable, TypeVar

tests/tensorizer_loader/test_tensorizer.py

+# SPDX-License-Identifier: Apache-2.0
+
 import gc
 import json
 import os

tests/test_cache_block_hashing.py

+# SPDX-License-Identifier: Apache-2.0
 """Test hashing of cache blocks.
 
 Run `pytest tests/test_cache_block_hashing.py`.

tests/test_config.py

+# SPDX-License-Identifier: Apache-2.0
+
 from dataclasses import asdict
 
 import pytest

tests/test_embedded_commit.py

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

tests/test_inputs.py

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

tests/test_logger.py

+# SPDX-License-Identifier: Apache-2.0
+
 import json
 import logging
 import os

tests/test_logits_processor.py

+# SPDX-License-Identifier: Apache-2.0
+
 import random
 from typing import Tuple
 from unittest.mock import patch