url: fix surrogate handling in encodeAuth()

Author: TimothyGu

lib/internal/url.js

@@ -577,6 +577,7 @@ function encodeAuth(str) {
     }
     // Surrogate pair
     ++i;
+    ++lastPos;
     var c2;
     if (i < str.length)
       c2 = str.charCodeAt(i) & 0x3FF;

test/parallel/test-url-format.js

@@ -235,6 +235,15 @@ const formatTests = {
     protocol: 'file',
     pathname: '/home/user',
     path: '/home/user'
+  },
+
+  // surrogate in auth
+  'http://%F0%9F%98%80@www.example.com/': {
+    href: 'http://%F0%9F%98%80@www.example.com/',
+    protocol: 'http:',
+    auth: '\uD83D\uDE00',
+    hostname: 'www.example.com',
+    pathname: '/'
   }
 };
 for (const u in formatTests) {