The federal government late Friday filed lawsuits against 17 financial intuitions, including some of the nation’s largest banks, alleging a pattern of fraud in their packaging and selling of roughly $200 billion worth of mortgage-linked securities. The suits amount to one of the most significant legal actions to emerge from the rubble of the financial crisis nearly three years ago.The allegations by the Federal Housing Finance Agency, which is seeking unspecified compensation, penetrate the heart of Wall Street’s role in helping lead the economy to ruin.