[region-isolation] Remove two sources of copying PartitionOps.

Was experimenting with making PartitionOps a noncopyable type and I discovered
these places where we copy PartitionOps when we could use a const reference. It
is good not to copy PartitionOps since they potentially contain a heap allocated
array.

Sadly, my change to make PartitionOps noncopyable will have to wait until a
forthcoming commit here I overhaul how we emit errors since that older code
copies PartitionOps a lot and I would rather just delete that code and then fix
PartitionOps. But these are on the surface safe changes that makes sense to get
in separately to make that next patch easier to review.

Author: gottesmm

include/swift/SILOptimizer/Utils/PartitionUtils.h

@@ -748,7 +748,7 @@ struct PartitionOpEvaluator {
   }
 
   /// Apply \p op to the partition op.
-  void apply(PartitionOp op) {
+  void apply(const PartitionOp &op) const {
     if (emitLog) {
       REGIONBASEDISOLATION_VERBOSE_LOG(llvm::dbgs() << "Applying: ";
                                        op.print(llvm::dbgs()));

lib/SILOptimizer/Mandatory/TransferNonSendable.cpp

@@ -1389,7 +1389,7 @@ class BlockPartitionState {
   bool recomputeExitFromEntry() {
     Partition workingPartition = entryPartition;
     PartitionOpEvaluator eval(workingPartition);
-    for (auto partitionOp : blockPartitionOps) {
+    for (const auto &partitionOp : blockPartitionOps) {
       // By calling apply without providing a `handleFailure` closure, errors
       // will be suppressed
       eval.apply(partitionOp);
@@ -1421,7 +1421,7 @@ class BlockPartitionState {
     os << "exit partition: ";
     exitPartition.print(os);
     os << "instructions:\n┌──────────╼\n";
-    for (PartitionOp op : blockPartitionOps) {
+    for (const auto &op : blockPartitionOps) {
       os << "│ ";
       op.print(os, true /*extra space*/);
     }