Grow a Garden's massive popularity has helped Roblox's stock hit record highs this year.Grow a Garden may not sound like the most exciting game to play on Roblox (RBLX -2.36%), but it's definitely the most popular. Last month, it reached a record of more than 22 million people playing it simultaneously. That blew past Fortnite's previous record of more than 15 million concurrent users. For Roblox, that's great news for business. More gaming means more purchases of its virtual currency, Robux. That leads to ...