dgram: add support for UDP connected sockets

Added the `dgram.connect()` and `dgram.disconnect()` methods that
associate/disassociate a udp socket to/from a remote address.
It optimizes for cases where lots of packets are sent to the same
address.
Also added the `dgram.remoteAddress()` method to retrieve the associated
remote address.

PR-URL: https://github.com/nodejs/node/pull/26871
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

test/parallel/test-dgram-connect-send-multi-string-array.js

@@ -0,0 +1,17 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const dgram = require('dgram');
+const socket = dgram.createSocket('udp4');
+const data = ['foo', 'bar', 'baz'];
+
+socket.on('message', common.mustCall((msg, rinfo) => {
+  socket.close();
+  assert.deepStrictEqual(msg.toString(), data.join(''));
+}));
+
+socket.bind(0, () => {
+  socket.connect(socket.address().port, common.mustCall(() => {
+    socket.send(data);
+  }));
+});