[11.x] Deprecate Factory::$modelNameResolver (#54736)

Instead of removing the `$modelNameResolver` property entirely,
 which breaks any user-land and 3rd-party uses of it,
 this re-introduces the original property, but marks it as
 deprecated so that developers have a chance to migrate
 correctly without having to avoid other Laravel updates.

Author: samlev

src/Illuminate/Database/Eloquent/Factories/Factory.php

@@ -113,6 +113,13 @@ abstract class Factory
      */
     public static $namespace = 'Database\\Factories\\';
 
+    /**
+     * @deprecated use $modelNameResolvers
+     *
+     * @var callable(self): class-string<TModel>
+     */
+    protected static $modelNameResolver;
+
     /**
      * The default model name resolvers.
      *
@@ -810,7 +817,7 @@ public function modelName()
             return $this->model;
         }
 
-        $resolver = static::$modelNameResolvers[static::class] ?? static::$modelNameResolvers[self::class] ?? function (self $factory) {
+        $resolver = static::$modelNameResolvers[static::class] ?? static::$modelNameResolvers[self::class] ?? static::$modelNameResolver ?? function (self $factory) {
             $namespacedFactoryBasename = Str::replaceLast(
                 'Factory', '', Str::replaceFirst(static::$namespace, '', $factory::class)
             );
@@ -931,6 +938,7 @@ protected static function appNamespace()
      */
     public static function flushState()
     {
+        static::$modelNameResolver = null;
         static::$modelNameResolvers = [];
         static::$factoryNameResolver = null;
         static::$namespace = 'Database\\Factories\\';