Move function signature analysis to a Util

We really only need this signature analysis in the cloner pass now.

Author: trentxintong

include/swift/SILOptimizer/Analysis/Analysis.def

@@ -30,7 +30,6 @@ ANALYSIS(ClassHierarchy)
 ANALYSIS(Destructor)
 ANALYSIS(Dominance)
 ANALYSIS(Escape)
-ANALYSIS(FunctionSignature)
 ANALYSIS(InductionVariable)
 ANALYSIS(Loop)
 ANALYSIS(LoopRegion)