[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/Providers/AppServiceProvider.php

@@ -8,20 +8,16 @@ class AppServiceProvider extends ServiceProvider
 {
     /**
      * Register any application services.
-     *
-     * @return void
      */
-    public function register()
+    public function register(): void
     {
         //
     }
 
     /**
      * Bootstrap any application services.
-     *
-     * @return void
      */
-    public function boot()
+    public function boot(): void
     {
         //
     }