Removed the "search_api_base_path" query option

In our Views integration, we added a search_api_base_path option to the search query in some situations so other modules could use it. However, this option was not actually used by anyone, as far as could be determined, but caused problems with caching. Therefore, it was removed in #3243313: Any view with a path is always cached per route. If you did need the option, please get its value from the view directly ($view->getPath()).