Make HardwareConcurrentTag base class of VectorizeTag

Make HardwareConcurrentTag base class of VectorizeTag, and update now-redundant isinstance(VectorizeTag, ConcurrentTag) checks.

I also made some notes in places where (Hardware)ConcurrentTag tags are being checked to point out that Vectorize tags are now included.

@inducer, are there other modifications that need to be included with this change? In particular, I was unsure about the write-race checking here and here

Also, should UniqueTag still be a base class of VectorizeTag?

If these changes should become part of my iname-sets-in-loop-priorities branch instead of being a separate merge request, let me know.