[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

app/Exceptions/Handler.php

@@ -38,10 +38,8 @@ class Handler extends ExceptionHandler
 
     /**
      * Register the exception handling callbacks for the application.
-     *
-     * @return void
      */
-    public function register()
+    public function register(): void
     {
         $this->reportable(function (Throwable $e) {
             //