SIL: SILUndef must be aware of the resilience expansion

The ownership kind is Any for trivial types, or Owned otherwise, but
whether a type is trivial or not will soon depend on the resilience
expansion.

This means that a SILModule now uniques two SILUndefs per type instead
of one, and serialization uses two distinct sentinel IDs for this
purpose as well.

For now, the resilience expansion is not actually used here, so this
change is NFC, other than changing the module format.

lib/SILOptimizer/Transforms/ConditionForwarding.cpp

@@ -259,7 +259,7 @@ bool ConditionForwarding::tryOptimize(SwitchEnumInst *SEI) {
     assert(ArgUser == SEI);
     // We delete the SEI later anyway. Just get rid of the Arg use.
     ArgUse->set(SILUndef::get(SEI->getOperand()->getType(),
-                              getFunction()->getModule()));
+                              *getFunction()));
   }
 
   // Redirect the predecessors of the condition's merging block to the