src: extract common sockaddr creation code

This commit extracts code to create sockaddr which is shared by both
UDPWrap::DoBind and UDPWrap::DoSend.

PR-URL: https://github.com/nodejs/node/pull/26070


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>