dgram: Implement binding an existing `fd`. Allow pass a `fd` property
to `socket.bind()` in dgram.
src: Add `UDPWrap::Open`
PR-URL: https://github.com/nodejs/node/pull/21745
Fixes: https://github.com/nodejs/node/issues/14961
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
