refactor(propagate): extract main logic into function to make it testable

src/pytorch_gum_uncertainty_propagation/examples/propagate.py

 """Does the actual propagation to be profiled for MLPs equipped with GUMQuadLU"""
 
-__all__ = ["assemble_pipeline"]
+__all__ = ["assemble_pipeline", "iterate_over_activations_and_architectures"]
 
 import datetime
 from itertools import repeat