private URL fileToURL(File file) {
    try {
      return file.toURI().toURL();
    } catch (MalformedURLException e) {
      throw new RuntimeException(e);
    }
  }
Visit all installed plugins.

@param visitor function to visit all installed plugins.
amoro-ams/src/main/java/org/apache/amoro/server/manager/AbstractPluginManager.java