ATLANTA — Georgia Democrats are building a formidable advantage in their battle to hold U.S. Sen. Raphael Warnock’s seat and flip other statewide races: a tidal wave of cash. Republicans, meanwhile, are slowly cobbling together their own mountain of moolah. Financial disclosures out this past week continued to cement Warnock as one of the nation’s elite fundraisers. The first-term Democrat set another financial record by raising $13.6 million over the first three months of the year, ending the quarter with $25.6 million in the bank. His top Republican rival, former football star Herschel Walke…