Support for os.sendfile for Windows

[KhazAkar]

Feature or enhancement

Currently, only POSIX operating systems have support for sendfile in python, but not Windows (or at least not on the same level, more about that later). There's a catch - windows also have support for this kind of functionality, called TransmitFile:
https://learn.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile

Pitch

Having this feature outside of asyncio (here it currently resides when using sock_sendfile, as link in "previous discussion" states) would help in closing the gap between what's supported on Windows and on POSIX OSes like macOS or Linux.
Basic support for things like overlapped I/O (Windows acronym for asynchronous I/O) currently exists in lower level modules, like undocumented _overlapped module. Having this exposed in more user-friendly manner would give python better feature parity between various Tier-1 operating systems.

Previous discussion

https://discuss.python.org/t/support-for-os-sendfile-for-windows/25020

[aisk]

I have a try on this, but found that there are some gaps between the *nix sendfile and Windows TransmitFile:

• If count + offset > file_size, sendfile will just send the rest of the file, and returns the byte which have been sent. The TransmitFile will raise a Windows error (and don't know how many bytes have been sent).
• TransmitFile use the overlapped IO stuff to make the timeout, and ignores the SO_SNDTIMEO socket option. Although Python don't use it to make timeout.

And the os.sendfile is just low level API, and most people are just using socket.sendfile in their codes.

So I think just implement the socket.sendfile via TransmitFile is a better idea, which already have a issue: #65920 , and if someone want a low level API, he can just using the Overlapped.TransmitFile.

cc @eryksun