CI: add valgrind job

Description

• Valgrind CI job based on CMake
• Moving to CMake implies enforcing a max. runtime of 1000 second per group of tests
• A unique temporary directory is defined per test to avoid openmpi race conditions (this has been implemented month ago). However, the directory was only defined but not created (openmpi can deal with that). Valgrind also tries do write to that directory but it fails if the TMPDIR directory does not exist. Therefore, we now create the directory before executing the test.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.