A trio of Federal Reserve officials who disagree deeply with one another over the appropriate stance of monetary policy on Friday expressed a shared distrust for using interest rates to head off asset bubbles and other forms of financial instability. Both Richmond Fed President Jeffrey Lacker, a policy hawk, and San Francisco Fed President John Williams, a centrist, told reporters after a policy conference here that they would not want to risk unmooring the public’s expectation that inflation will rise back to the Fed’s 2 percent goal in the next few years.