[!280] Avoid visiting No-op integrals

Merge branch 'feature/avoid-visiting-noop-integrals' into 'master'

ref:dominic/dune-perftool I have a case where visiting has a side effect that
I want to avoid. Also spares work.

See merge request [dominic/dune-perftool!280]

  [dominic/dune-perftool!280]: gitlab.dune-project.org/dominic/dune-perftool/merge_requests/280