Upgraded PETSc minimum to 3.18.6.

See merge request !4849

Workarounds for 3.16 can be reverted.
3.16 does not build on recent Arch, make 4.4.1, see

https://gitlab.com/petsc/petsc/-/merge_requests/6140

Update JUWELS module loading using Stage/2024

See merge request !4838

[ci] Fixes

See merge request !4845

[cff] Added author orcids

See merge request !4836

This reverts commit 3d057997 which broke
benchmark downloads.

[ci] PETSc pkg-config fixes

See merge request !4844

[py] Import OpenGeoSys module properly

See merge request !4843

mtest / tfel python bindings are not available on the test machines
and are therefore skipped.

Affects ModCamClay_TestIsotrop.ipynb.

Needs to be imported with:

try:
    import ogs.callbacks as OpenGeoSys
except ModuleNotFoundError:
    import OpenGeoSys

`ogs.callbacks` is needed when imported via pip installed package.
`import OpenGeoSys` else.

Tests thermo poro elasticity relax tolerance

See merge request !4841

[nb] Make tfel available

See merge request !4842

[cmake] Simplify PETSc finding

See merge request !4839

[cmake] Use VTK 9.3 on gcc 13.2.

See merge request !4840

Fixes compile errors in VTK.

This is now recommended. See

https://lists.mcs.anl.gov/pipermail/petsc-users/2019-December/039937.html

FindPETSc.cmake was used.

[cmake] Refactor netCDF library finding

See merge request !4814

Code cleanup: Move code from NumLib to MathLib

See merge request !4833

BHE 1P Benchmark fixes

See merge request ogs/ogs!4834