Credit Suisse, the collapsed Swiss bank taken over by UBS Group in a hastily arranged bailout earlier this month, may bring with it a fresh set of regulatory and legal problems for its new owner. For years, the bank has provided a safe haven for wealthy American clients to hide assets from the IRS — even after it was caught and prosecuted for doing the same thing more than a decade ago, according two former Credit Suisse bankers who spoke in exclusive interviews with CNBC and are working with the U.S. government as whistleblowers. The bank notoriously pleaded guilty in 2014 to criminal charges for “knowingly and willfully” helping thousands…