There is no water. There is no power. There is no Wi-Fi. There is no parking. But there also are no neighbor hassles. Red Rock Island, a 6-acre outcropping that is touted as the last private island on San Francisco Bay, is going on the market this week for $25 million, according to its listing agent. Though the island has been for sale before and has been considered for every possible isolated use, from a rocky top Playboy Club to a wind farm, this is the first time it has been included on a multiple listing service, a database that allows brokers to see other agents’ listings.