Rework socket (#5545)

* Extract _socket.pyi from socket.pyi.
* Extract _socket.socket from socket.socket.
* Fix socket.family annotation.
* Annotate SocketIO properly.
* SocketType is an alias of _socket.socket.
* Sort items in socket.pyi in the same order as in socket.py.
* Remove socket.EINTR.
* Use _typeshed.WriteableBuffer instead of custom alias.
* Add errorTab (Windows only).
* Add _socket.dup().
* Mark positional-only argments.
* Remove constructors from socket exceptions.
* socket.timeout is an alias for TimeoutError, starting with Python 3.10.
* Use PEP 604 in changed lines.
* Add alias for fileno arguments.
* getaddrinfo() port can be bytes.
* Explicitly override some SSLSocket methods.
* Allow ReadableBuffer in _CMSG arguments.

tests/stubtest_whitelists/py3_common.txt

@@ -12,6 +12,7 @@ _collections_abc.Mapping.get  # Adding None to the Union messed up mypy
 _collections_abc.Sequence.index  # Supporting None in end is not mandatory
 _csv.Dialect.__init__  # C __init__ signature is inaccurate
 _dummy_threading
+_socket.*
 _threading_local.local.__new__
 _typeshed.*  # Utility types for typeshed, doesn't exist at runtime
 abc.abstractclassmethod