[ISTLBackend] Compatibility with allocator-aware DynamicVector

After 2.3, DynamicVector got support for allocators, changing the
template signature of the type. We thus need to distinguish between
dune-common 2.3 and older, where DynamicVector only takes a single
template parameter, and later versions, where there are two.
[RannacherTurekFEM] Bring RannacherTurekFEM up to date and provide dimension-independent class

The Rannacher-Turek element in dune-localfunctions was changed to work
in a dimension-independent way during the 2.3 release cycle. As the old
version of the element has been deprecated, we need to switch to the new
one.

We also grab the chance and make the FEM frontend class
dimension-independent as well, deprecating the old 2D version.
[Tests] Add test for new RannacherTurekLocalFiniteElementMap

The test instantiates the FEM for 2D and 3D.