While at first sight just a superficial variation of the existing IterStateWrapper,
it became clear with the evolution of the IterExplorer framework that
this setup represents a distinct concept, and especially lends itself
for complex and cohesive collaboration in a layered pipeline. Which
may, or may not be a good idea, depending on the circumstances.
Now, for the implementation of the scheduler memory allocation scheme,
another twist is added to the picture: we can not effort the sanity checks
on each access, even more so when layering / adapting iterators, where
it is essential that the optimiser can remove all unnecessary warts.