Draft: AST-1370: Reimplementation of H5 facet solutions cache with xtensor.

• Draft merge request, no code style included.
• Please, analyze the general implementation.
• Verify this implementation works for H5 files different from those used for reproduce the problem.
• To test WSClean using this branch, pull this WSClean branch: https://gitlab.com/aroffringa/wsclean/-/tree/ast-1370-applying-h5parm-solutions-painfully-slow It should use download this branch of schaapcommon under 'external' directory.