gh-135748: Use Argument Clinic for more socket functions

[serhiy-storchaka]

Convert all convertible functions and methods of the socket module to Argument Clinic. They now have signatures for introspection, and functions which take several arguments use METH_FASTCALL instead of METH_VARARGS.

The number of _socket callables for which inspect.signature() fails drops from 26 to 7. Five of those seven are deliberate: listen() (the default is Py_MIN(SOMAXCONN, 128)), getservbyname() and getservbyport() (the C default is NULL and None is not accepted), sendmsg() and sendmsg_afalg() (arguments which are absent rather than defaulted).

ioctl(), sendto() and setsockopt() are left as they are. Their behaviour depends on the number of the arguments or on the value of a preceding argument, which Argument Clinic cannot express:

• sendto(data[, flags], address) -- the optional argument is in the middle, while optional groups only support [left] required [right].
• setsockopt() distinguishes 3 from 4 arguments with PyTuple_Size(), and both resulting error messages are asserted by test_socket.
• ioctl() parses its second argument differently depending on cmd.

The parameter names are taken from the existing docstrings. Seven of them differ from Doc/library/socket.rst (for example recv(buffersize) versus the documented bufsize); the documentation is left unchanged here.

• Issue: use argument clinic for more socket functions #135748