[11.x] Declare bindings and singletons properties in Service Provider (#52256)

* Declare bindings and singletons "magick" properties

* Update ServiceProvider.php

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: Anton5360

src/Illuminate/Foundation/Application.php

@@ -870,18 +870,14 @@ public function register($provider, $force = false)
         // If there are bindings / singletons set as properties on the provider we
         // will spin through them and register them with the application, which
         // serves as a convenience layer while registering a lot of bindings.
-        if (property_exists($provider, 'bindings')) {
-            foreach ($provider->bindings as $key => $value) {
-                $this->bind($key, $value);
-            }
+        foreach ($provider->bindings as $key => $value) {
+            $this->bind($key, $value);
         }
 
-        if (property_exists($provider, 'singletons')) {
-            foreach ($provider->singletons as $key => $value) {
-                $key = is_int($key) ? $value : $key;
+        foreach ($provider->singletons as $key => $value) {
+            $key = is_int($key) ? $value : $key;
 
-                $this->singleton($key, $value);
-            }
+            $this->singleton($key, $value);
         }
 
         $this->markAsRegistered($provider);

src/Illuminate/Support/ServiceProvider.php

@@ -19,6 +19,20 @@ abstract class ServiceProvider
      */
     protected $app;
 
+    /**
+     * All of the container bindings that should be registered.
+     *
+     * @var array
+     */
+    public $bindings = [];
+
+    /**
+     * All of the singletons that should be registered.
+     *
+     * @var array
+     */
+    public $singletons = [];
+
     /**
      * All of the registered booting callbacks.
      *