gh-141968: Use take_bytes to remove copy in _pyio.BytesIO.read()

[lgeiger]

This removes a copy going from bytearray to bytes in _pyio.BytesIO.read().

import timeit
from statistics import mean, stdev

times = timeit.repeat(
    "bio.seek(0); bio.read()",
    setup="import _pyio; bio = _pyio.BytesIO(b'x' * 1024 * 1024)",
    number=50_000,
    repeat=5,
)
print(f"{mean(times) * 1e3:.2f} ± {stdev(times) * 1e3:.2f} ms")

main:    1403.29 ± 14.36 ms
this PR: 785.91 ± 4.27 ms 

• Issue: Remove bytearray to bytes copies in stdlib using take_bytes #141968

[lgeiger]

As far as I can tell b = self._buffer[self._pos : newpos] already copies the bytearray so we can safely use take_bytes()

[maurycy]

cc @cmaloney