A pattern that we have been manually implementing in quite some places!

This is not used anymore since we have mixins.

This reverts commit 6a1e7cc9

This reverts commit f83a804e

As a side effect we removed the dune-testtools dependency.

consecutive means the tail is within the same subelement inames as
the vectorized loop (except for the vectorized iname)
blocked means each tail has its on set of subelement inames