Extend HPO-Sampling

[mali-git]

In this PR, we extend the HPO-sampling, so that parameters of the entity_representation, relation_representation, and interaction modules can be sampled.

[cthoyt]

Almost all of the existing HPO model is generally applicable to all models. I'm a bit skeptical of these additions because they're pretty specific for a small (albeit important) subset of models. Before further review, I think it's important to motivate the addition of such complexity to the existing HPO model through a series of narrative examples as well as adding reference documentation (i.e., pass CI).

I think it might be the case that this motivates creating a new HPO workflow, so do carefully write up explanations for everything here so we can consider splitting it out.

[mberr]

Once the remaining models from https://github.com/pykeen/pykeen/projects/1 are upgrade to ERModel, all models will support this; so maybe it is time update the {hpo_}pipeline afterwards.

[cthoyt]

Looking back, I'm still thinking this increases complexity too much. I'm going to close this, but if anyone wants to take a careful look again, we can re-open it.