Build rules for Ubuntu Jammy with OpenZGY using clang++ and c++20. Still using...

Fix issues and warnings seen when building with with clang and C++20. Most of the changes have been contributed by Jon Jenssen. See issue #26 (closed).

Add build rules for Ubuntu Jammy with OpenZGY built with clang. SDAPI and dependencies are still built with the gnu compilers. The new configuration has been added to the build pipelines run internally in SLB. There are currently no scheduled builds in OSDU / GitLab.