Check Tags instanceof check before iterator empty check in Tags.of()

[izeye]

This PR changes to check Tags instanceof check before iterator empty check in Tags.of() to save ArrayIterator creation.

[shakuzen]

Thanks. I had in my notes to make this change, but I was curious to benchmark if there's a noticeable difference with this. I haven't had a chance yet to look into it more deeply, but on the surface it certainly seems worth avoiding the allocation if we can.

[shakuzen]

I still haven't had a chance to do the deeper dive I wanted on this and similar changes. I don't expect it would cause any problem, but I'll hold off on merging it until next release.