Move System::jsonError to BaseModule->jsonError

- This will ensure headers set in BaseModule->run will be carried in jsonError scenarios
- Make BaseApi->checkThrottleLimit an object method to use BaseModule->jsonError
- Deprecate jsonError() method in Core\System

src/Core/System.php

@@ -373,6 +373,9 @@ class System
 		self::exit();
 	}
 
+	/**
+	 * @deprecated since 2023.09 Use BaseModule->jsonError instead
+	 */
 	public static function jsonError($httpCode, $content, $content_type = 'application/json')
 	{
 		if ($httpCode >= 400) {