[issue32529] Call readinto in shutil.copyfileobj

[YoSTEALTH]

YoSTEALTH <ritesh at stealthcentral.com> added the comment:

Ok, updated the patch to account for:
- improved memory usage for bytes io using readinto
- still supporting negative length
- potential encoding mismatch bug fix while using text io

did i miss anything?

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue32529>
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