Create integration tests for Everest based on the tutorials

[verveerpj]

Is your feature request related to a problem? Please describe.
We currently do not have integration tests that cover the main applications that Everest is used for, in particular testing the interaction with the forward models in everest-models.

Describe the solution you'd like
The existing tutorials should be turned into integration tests. These do not necessarily have to run within the Everest test-set and/or on every PR. It should be possible to run them regularly, for instance nightly, but it should also be easy to start them manually when needed.

Describe alternatives you've considered
N/A

Additional context

• Running regularly could be done via GitHub actions or any other approach that would work with Equinor resources. At TNO we would like to be able to start them infrequently (manually) on our SLURM cluster.
• Look into existing similar cases, such as the HM tutorial.
• The tutorials could be slow, in which case we should consider versions that are 'cut short' for nightly runs and run full version less regularly.
• We may need to rework the tutorials to use OPM flow, using a licensed software would not be convenient.
• We should use the tests to check if results are still fully in agreement with the tutorials. Small changes in the results may be due to harmless software changes, such as new simulator versions. However, the tutorials may need to be updated to reflect that.