Discussion: use global evolution in test_integration_features.py

Currently, our `test_integration_features.py` is slow as it calls only `run_coeval` and `run_lightcone`. We could reduce runtime of some of the tests if we call `run_global_evolution` instead. This will of course shorten the runtime significantly, but it will limit us as we won't be able to compare fluctuations/power spectrum with what we have in the database.