function flattenRcToConfig(rc) {
  return {
    ...(rc.ci || {}),
    ...(rc.lhci || {}),
    ..._.omit(rc['ci:client'] || {}, ['server']),
    ..._.pick(rc['ci:server'] || {}, ['server']),
  };
}
@param {LHCI.LighthouseRc} rc
@return {LHCI.LighthouseCiConfig}