A spate of dire warnings from retailers last week, including Walmart Inc WMT.N and Target Corp TGT.N raised such concerns. By Stephen Culp NEW YORK, May 23 (Reuters) - Wall Street rallied on Monday as gains from banks and recently battered megacap market leaders helped U.S. stocks rebound after their longest streak of weekly declines since the dotcom bust. Markets have been roiled in recent weeks by worries about persistently high inflation and aggressive attempts by the Federal Reserve to rein it in while the global economy copes with fallout from Russia's invasion of Ukraine.