Enable reflected I/O for StrongTypes

See merge request ogs/ogs!5004

Enable Volumetric and Python source terms on 0D elements (aka Points)

See merge request ogs/ogs!5009

Computing shape matrices of a d-dimensional Element in less than d
dimensions is not meaningful.

With that change "Volumetric"/"Python" source terms can be applied to nodes, as well.
Thereby, the special "Nodal" source term has become obsolete, now.

B bar method for linear deformation

See merge request ogs/ogs!5007

HoekBrown and a MFront test

of the function to comput B_dil_bar matrix, and some other minor changes

[ci] Fix linux wheel builds

See merge request ogs/ogs!5014

See https://github.com/pypa/manylinux:

From manylinux2014 to manylinux_2_28. Requires pip 20.3.

Does not compile with gcc 10.2 anymore after !4992. See e.g.
https://gitlab.opengeosys.org/ogs/ogs/-/jobs/442490.

Currently envinf4 and envinf5.

Vectorial exprtk function arguments

See merge request ogs/ogs!4992