[!781] Allow iterator based transformations in TransformedRangeView

Merge branch 'feature/extend-transformedrangeview' into 'master'

ref:core/dune-common\> This extends TransformedRangeView by also allowing to
apply a transformation to the iterator directly. While the (existing) default
mechanism is to use f(*it) where f is the transformation and it an iterator of
the wrapped range, the new iterator based transformation uses f(it) instead.
This allows to incorporate additional information from the iterator in the
transformation.

Using the new functionality one can e.g. easily implement structured bindings
support for sparse ranges using

    template<class Range>
    auto sparseRange(Range&& range) {
      return Dune::transformedRangeView(std::forward<Range>(range), Dune::taggedCallback<Dune::IteratorTransformationTag>([](auto&& it) {
          return std::tuple<decltype(*it), decltype(it.index())>(*it, it.index());
      }));
    }

    ...

    for(auto&& [entry,col] :  sparseRange(matrix[row]))
      y[row] += entry*x[col];

Some more implementation details:

-   This adds the TaggedCallback<Tag,F> helper class and the corresponding
    generator function taggedCallback<Tag>(f) for tagging a callback. Using
    this mechanism we can provide additional information on the callback.
-   If the TransformedRangeView is provided with a callback of type
    TaggedCallback<IteratorTransformation,F>, then it iterator based
    transformation is used.

See merge request [core/dune-common!781]

  [core/dune-common!781]: gitlab.dune-project.org/core/dune-common/merge_requests/781