message: Clarify compression remat's names.
  Clarify compression remat's names so we don't confuse them with layout assignment copies.
diff: @@ -1524,9 +1524,11 @@ StatusOr<int64> CompressInstruction(MemoryUsageTracker* memory_tracker,
  HloInstruction* compressed = computation->AddInstruction(
  HloInstruction::CreateUnary(compact_shape, HloOpcode::kCopy, best));
  + compressed->SetAndSanitizeName(best->name() + ".remat_compressed");
  HloInstruction* uncompressed = computation->AddInstruction(
  HloInstruction::CreateUnary(best->shape(), HloOpcode::kCopy, compressed));
  + uncompressed->SetAndSanitizeName(best->name() + ".remat_uncompressed");
  Item* compressed_item = instruction_list->CreateItem(compressed);
  compressed_item->placed = true;
  