[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/Feature/ExampleTest.php

@@ -9,10 +9,8 @@ class ExampleTest extends TestCase
 {
     /**
      * A basic test example.
-     *
-     * @return void
      */
-    public function test_the_application_returns_a_successful_response()
+    public function test_the_application_returns_a_successful_response(): void
     {
         $response = $this->get('/');