Checking len bounds after usage in bytesio.c

[naya451]

In _io_BytesIO_readinto_impl() len value is used in memcpy and then checked for being positive.
It's better to move assertions before memcpy.

This may be done with the following commit: da720c1

Linked PRs

• gh-131505: Move len boundary assertions before using len. #131536
• [3.14] gh-131505: Move len boundary assertions before using len. (GH-131536) #134239

[corona10]

Sounds reasonable please submit the patch.

[gpshead]

thanks!