[Task] Replace EngineTestHelper with Engine

[SarahAlidoost]

After #25, we have to replace EngineTestHelper with Engine. Apply changes in:

• crop modules
• notebooks
• tests
• dont fix import from parameter_provider in notebook, check if related fix has been merged in pcse, see Run multiple crops - first work on engine #124
• Also fix changes introduced by Move test helpers to dedicated module #125 in all notebooks, import from utils should be replaced by import from test