add gmres restart test1

set gmres restart test2

add restart option for all Preconditioners (final)

Add prism element type to structure mesh generator tool.

Add bulk element mappings for triangles.

Clang-tidy cleanups.

This is necessary because of a doxygen bug in
documenting overloaded functions.

Fix cppcoreguidelines-pro-type-member-init.

Fix cppcoreguidelines-pro-type-member-init.

Fix google-readability-braces-around-statements.

Fix warning cppcoreguidelines-pro-type-member-init.

Van Genuchten capillary pressure saturation

Thanks to @Scinopode for reporting.

Cleanup

Points were accessed and moved in a for-loop. Second
iteration would result in access after move.

No occurence of OGS_FATAL in that file.

No INFO/ERR/WARN/DBUG calls in this files.

The fmt library happily accepts std::string without
any conversions.