[CMake] Added arguments PYTHON_PACKAGES and WORKING_DIRECTORY_SOURCE to AddTest()

Default working directory for tests was changed from source to binary dir.

- PYTHON_PACKAGES allows for specification of additional Python module dependencies. Requires the poetry-tool and specifying the 'poetry'-wrapper.
- WORKING_DIRECTORY_SOURCE reverts to previous behavior of running the tests in the source tree. Also adapted MeshTest() for this.