Previously this wouldn't compile, because GlobalP2Mapper only supported
1d and 2d grids when used without dune-parmg.  This has now been fixed,
so we can enable filmonsubstratetest and filmonsubstratetest-mixed
(which involve a 3d grid) also for the situation without dune-parmg.

Strangely, the test without the -mixed produces different results
depending on whether the dune-parmg version of GlobalP2Mapper is used
or not. Minor differences are to be expected because the precise
behavior of multigrid methods (which are used by the TR solver) depends
on the dof ordering.  But the difference seen here is a bit large
for my taste.

I don't quite understand this, so this commit introduces some
subcasing to make CI pass, and document the current behavior.

Plus some minor cleanup

Rather than using preprocessor switches.  That's too fragile
and not extensible.

If the target manifold is a product space, then ProductManifold must be
used, and not a variadic list of the factor space types.

Together with the new test, this commit also contains a number
of fixes for the SurfaceCosseratEnergy class.  This class was
not unit-tested previously, and unintentionally I messed it up
badly during my recent modernization work.

Finally, SurfaceCosseratEnergy had apparently never been tested
without dune-curvedgeometry, which is however only an optional
dependency.  The commit therefore also adds the necessary
conditionals.

Then problem then is that the derivative of the outer normal
of an intersection is not available from the standard grid interface.
If dune-curvedgeometry is not available, this derivative is
simply set to a zero matrix.  Depending on the grid manager
this may not actually be correct, though.