CI: add valgrind checks for test domain

In this merge request an addition to CI is proposed:

• another CI script is added to compile mhm in debug mode
• a mhm run for the test domain is checked with the valgrind tool memcheck to check for memory errors
• a mhm run for the test domain is checked with the valgrind tool massif to analyze memory consumption
• massif output is stored as artifact massif.out.0 from job valgrind-mem-use
• gfortran compiled executable is stored as artifact mhm from job compile-gfortran83