Issue #24684: socket.socket.getaddrinfo() now calls

Issue #24684: socket.socket.getaddrinfo() now calls
PyUnicode_AsEncodedString() instead of calling the encode() method of the
host, to handle correctly custom string with an encode() method which doesn't
return a byte string. The encoder of the IDNA codec is now called directly
instead of calling the encode() method of the string.