Add critical edge verification and fix SIL passes.

SIL passes were violating the existing invariant on non-cond-br
critical edges in several places. I fixed the places that I could
find.  Wherever there was a post-pass to "clean up" critical edges, I
replaced it with a a call to verification that the critical edges
aren't broken in the first place.

We still need to eliminate critical edges entirely before enabling
ownership SIL.

lib/SILOptimizer/LoopTransforms/COWArrayOpt.cpp

@@ -2376,9 +2376,8 @@ class SwiftArrayOptPass : public SILFunctionTransform {
       for (auto &HoistableLoopNest : HoistableLoopNests)
         ArrayPropertiesSpecializer(DT, LA, HoistableLoopNest).run();
 
-      // We might have cloned there might be critical edges that need splitting.
-      splitAllCriticalEdges(*getFunction(), true /* only cond_br terminators*/,
-                            DT, nullptr);
+      // Verify that no illegal critical edges were created.
+      getFunction()->verifyCriticalEdges();
 
       LLVM_DEBUG(getFunction()->viewCFG());