gh-129813, PEP 782: Use PyBytesWriter in FileIO.read()

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Replace PyBytes_FromStringAndSize(NULL, size) and _PyBytes_Resize() with the new public PyBytesWriter API.

• Issue: [C API] PEP 782: Add PyBytesWriter API #129813

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Benchmark:

import pyperf
import os

file = open(__file__, "rb", 0)
def func():
    file.seek(0)
    for _ in range(100):
        file.read(1)

runner = pyperf.Runner()
runner.bench_func('bench', func)

file.close()

Result: Mean +- std dev: [ref] 65.8 us +- 1.0 us -> [change] 63.2 us +- 1.0 us: 1.04x faster

cc @cmaloney

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Merged. Thanks for the review @cmaloney.