Draft: Patch code generators to work with pre-release versions of pystencils 2.0
This MR introduces a number of compatibility patches to make the pystencils/lbmpy integration of waLBerla work with the changes coming with pystencils 2.0 (New type system, new code generation backend, various API deprecations and changes).
Most notably, the pystencils_walberla.compat
module is introduced to consolidate the most strongly divergent APIs.