Added PROPERTIES argument to AddTest(), OgsTest() and NotebookTest() and more...

• Test properties can now directly be set. Simplifies CMake logic a bit and is potentially more powerful.
• Refactored PyVista in notebooks testing logic: no special treatment for headless systems. User is responsible for providing a window environment, e.g. via xvfb-run, which is shortly documented.
• Added documentation on how to shorten pipeline run times by modifying the corresponding files.
• Added pipeline variable CTEST_INCLUDE_REGEX which corresponds to the -R ctest argument.

1. Feature description was added to the changelog
2. Tests covering your feature were added?