https: make opts optional & immutable when create

`opts` in `createServer` will be immutable that won't change origional
opts value. What's more, it's optional which can make `requestListener`
be the first argument.

Refs: #13584

doc/api/https.md

@@ -46,7 +46,7 @@ added: v8.0.0
 
 See [`http.Server#keepAliveTimeout`][].
 
-## https.createServer(options[, requestListener])
+## https.createServer([options][, requestListener])
 <!-- YAML
 added: v0.3.4
 -->

lib/https.js

@@ -34,6 +34,12 @@ const { urlToOptions, searchParamsSymbol } = require('internal/url');
 function Server(opts, requestListener) {
   if (!(this instanceof Server)) return new Server(opts, requestListener);
 
+  if (typeof opts === 'function') {
+    requestListener = opts;
+    opts = undefined;
+  }
+  opts = opts ? util._extend({}, opts) : {};
+
   if (process.features.tls_npn && !opts.NPNProtocols) {
     opts.NPNProtocols = ['http/1.1', 'http/1.0'];
   }

test/parallel/test-https-immutable-options.js

@@ -0,0 +1,22 @@
+'use strict';
+
+const common = require('../common');
+
+const assert = require('assert');
+const https = require('https');
+const tls = require('tls');
+
+const dftProtocol = {};
+tls.convertNPNProtocols([ 'http/1.1', 'http/1.0' ], dftProtocol);
+
+const opts = { foo: 'bar' };
+const server1 = https.createServer(opts);
+
+assert.deepStrictEqual(opts, { foo: 'bar' });
+assert.strictEqual(server1.NPNProtocols.compare(dftProtocol.NPNProtocols), 0);
+
+const mustNotCall = common.mustNotCall('dummy callback');
+const server2 = https.createServer(mustNotCall);
+
+assert.strictEqual(server2.NPNProtocols.compare(dftProtocol.NPNProtocols), 0);
+assert.strictEqual(mustNotCall, server2._events.request);