Implement use of monitor flag for liesel.models

[wiep]

I've implemented a hacky version to support the monitor flag specified in a liesel model in goose's EngineBuilder. It is not in the final stage because I want to try the implementation before creating a new Protocol class.

~~Currently, the change makes the test test_sample_transformed_model in tests/model/test_goose.py fail. I assume that is because the tuning requires the key to be tracked mu_value is not tracked.~~