Unable to add new items via layout builder block update form

It seems that FormState::isSubmitted works somewhat differently within layout builder.

Perhaps instead of relying on FormState::isSubmitted as a flag to remove the additional, empty option, we could instead use our own property set on the form state that achieves the same goal?

Let's see what the test bot thinks...and while it's doing that, I'm going to run through more manual testing.

Update the patch to cover cases where more than one unlimited cardinality field might exist on the same form.

Clean up some odd formatting issues. Not quite sure how the top lines were re-indented...blame solar flares? :-)

Setting to NR - seems pretty solid to me.