[NFC]: add a FrontendStatsTracer for definite init

Author: jamieQ

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -3868,6 +3868,9 @@ static void processMemoryObject(MarkUninitializedInst *I,
 /// properly set and transform the code as required for flow-sensitive
 /// properties.
 static bool checkDefiniteInitialization(SILFunction &Fn) {
+  FrontendStatsTracer StatsTracer(Fn.getModule().getASTContext().Stats,
+                                  "definite-init", &Fn);
+
   LLVM_DEBUG(llvm::dbgs() << "*** Definite Init visiting function: "
                           <<  Fn.getName() << "\n");
   bool Changed = false;