gh-156939: Detect buffer overflow in bytearray

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Add bytearray_check_consistency() and
bytearray_check_trailing_null_byte() functions in call them in most bytearray methods.

• Issue: C API: Detect buffer overflow in PyBytesWriter #156939

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Tests / Sanitizers / TSan (pull_request): Failing after 13m

It's a legit bug:

WARNING: ThreadSanitizer: data race (pid=15518)
  Write of size 8 at 0x55b013af2f80 by main thread:
    #0 __tsan_memcpy <null> (python+0xfc452) (BuildId: 77d4ccbb4bf7bb80d66adcdbb8a43d9cd1f555bc)
    #1 set_allocator_unlocked /home/runner/work/cpython/cpython/Objects/obmalloc.c (python+0x38417f) (BuildId: 77d4ccbb4bf7bb80d66adcdbb8a43d9cd1f555bc)
    #2 PyMem_SetAllocator /home/runner/work/cpython/cpython/Objects/obmalloc.c:1143:5 (python+0x38417f)
    (...)

I reported the failure as #157415 and I proposed a fix (skip the test if TSAN is used).

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The PR adds bytearray_check_consistency(). Python has similar functions for other types:

• any Python object: _PyObject_CheckConsistency()
• type: _PyType_CheckConsistency()
• dict: _PyDict_CheckConsistency()
• str: _PyUnicode_CheckConsistency()
• PyWideStringList C API: _PyWideStringList_CheckConsistency()

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@cmaloney: Would you mind to review this change?

I didn't measure the overhead on runtime benchmark of a Python debug build. If bytearray_check_consistency() overhead is too high, the PR can be limited to add bytearray_check_buffer_overflow() assertions.

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I just made a similar change to detect buffer overflow in PyBytesWriter: PR gh-156943.