Add a GeodesicFEAssemblerWrapper - it wraps a MixedGFEAssembler so it can be...

Add a GeodesicFEAssemblerWrapper - it wraps a MixedGFEAssembler so it can be used like a GeodesicFEAssembler

The GeodesicFEAssemblerWrapper assembles the Gradient and the Hessian using the MixedGFEAssembler and then resturctures them so they can be used with the normal RiemannianTRSolver. This only works, if the FE spaces have the same order.

@osander: Can you already merge this? I've resolved the comments from yesterday.

enabled an automatic merge when the pipeline for aa03e106 succeeds

The 2.6 CI pipeline needs https://gitlab.dune-project.org/core/dune-istl/-/merge_requests/402 .

ok ... then I wait for this MR

It's in now.

canceled the automatic merge

merged

mentioned in commit f4b95381