[CopyPropagation] Only delete if canonicalized.

Owned lifetime canonicalization bails on move-only values.

Previously, though, every value that was fed to canonicalization was
then attempted to be deleted.  For dead move-only values, the result
could be to shorten move-only lifetimes, which is illegal per language
rules.

Here, this is fixed by not attempting to delete owned values for which
canonicalization bailed.

rdar://114323803

lib/SILOptimizer/Transforms/CopyPropagation.cpp

@@ -617,7 +617,9 @@ void CopyPropagation::run() {
   // Canonicalize all owned defs.
   while (!defWorklist.ownedValues.empty()) {
     SILValue def = defWorklist.ownedValues.pop_back_val();
-    canonicalizer.canonicalizeValueLifetime(def);
+    auto canonicalized = canonicalizer.canonicalizeValueLifetime(def);
+    if (!canonicalized)
+      continue;
     // Copies of borrowed values may be dead.
     if (auto *inst = def->getDefiningInstruction())
       deleter.trackIfDead(inst);