avoiding STL iterators.

No measurable run-time difference.

Default vtk 9.3.0 download misses ThirdParty/eigen/vtkeigen
subdirectory. Use explicit download from GitHub-tag.

[ci] Update guix channels.

See merge request ogs/ogs!5031

vtk 9.3 is now in upstream: https://issues.guix.gnu.org/70323

[NL] Remove matrix/vector types from NR interface

See merge request ogs/ogs!5027

Some CMake logic for building with conda

See merge request ogs/ogs!5029

Install functionality is skipped on conda builds.

The types for the jacobian matrix and the residual vector are not needed
in the NewtonRaphson class interface, only in the interior and can be
(mostly) deduced from the JacobianMatrixUpdate and ResidualUpdate first
function argument.

MeshLib error message improvements

See merge request ogs/ogs!5028

Another figure display fixing on the web page of Cook's membrane example

See merge request ogs/ogs!5022

Add mpirun to container

See merge request ogs/ogs!5024

[cmake,guix] Guix package includes OGS_USE_NETCDF=ON.

See merge request ogs/ogs!5023

Somehow this works around duplicated image size...

RichardsMechanics refactoring step 3

See merge request ogs/ogs!5017

 cooks_membrane.png