Bench only disables the plugins that it knows about

Currently, bench proactively disables all plugins besides the user-provided list that it knows about. This is problematic, because if a plugin has been removed from HLS, then bench will no longer know about it, and can no longer disable it. A possible way to fix this would be for HLS to have a configuration to allow a whitelist of plugins to enable, instead of a blacklist that they do now.