[10.x] Uses PHP Native Type Declarations 🐘 (#6010)

* Adds basic typing around method's arguments and return types

* Adds missing `closure` type

* Adds typing on tests

* Fixes `RedirectIfAuthenticated`

* Fixes `Authenticate`

* Improves `RedirectIfAuthenticated` types

* Fixes user factory `unverified` return type

tests/CreatesApplication.php

@@ -3,15 +3,14 @@
 namespace Tests;
 
 use Illuminate\Contracts\Console\Kernel;
+use Illuminate\Foundation\Application;
 
 trait CreatesApplication
 {
     /**
      * Creates the application.
-     *
-     * @return \Illuminate\Foundation\Application
      */
-    public function createApplication()
+    public function createApplication(): Application
     {
         $app = require __DIR__.'/../bootstrap/app.php';