lib: remove internal util._extends() usage

This removes all internal calls to the deprecated `_extends()`
function. It is slower than `Object.assign()` and the object spread
notation since V8 6.8 and using the spread notation often also
results in shorter code.

PR-URL: https://github.com/nodejs/node/pull/25105
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/https.js

@@ -46,7 +46,7 @@ function Server(opts, requestListener) {
     requestListener = opts;
     opts = undefined;
   }
-  opts = util._extend({}, opts);
+  opts = { ...opts };
 
   if (!opts.ALPNProtocols) {
     // http/1.0 is not defined as Protocol IDs in IANA
@@ -110,9 +110,10 @@ function createConnection(port, host, options) {
     const session = this._getSession(options._agentKey);
     if (session) {
       debug('reuse session for %j', options._agentKey);
-      options = util._extend({
-        session: session
-      }, options);
+      options = {
+        session,
+        ...options
+      };
     }
   }
 
@@ -292,7 +293,7 @@ function request(...args) {
   }
 
   if (args[0] && typeof args[0] !== 'function') {
-    options = util._extend(options, args.shift());
+    Object.assign(options, args.shift());
   }
 
   options._defaultAgent = globalAgent;