🧼🫧 Fix shape handling in Interaction

[mberr]

This MR cleans up inconsistencies in how we handle symbolic shapes in Interaction.

It now uses entity_shape as the shape information for all entity representations (head & tail). head_indices and tail_indices can be used to derive the shapes for a given role, exposed as properties head_shape and tail_shape.

It also lifts the restriction of only using interactions with shared head and entity shape via the interaction + dimensions API inside pipeline, and converts the class method get_dimensions to an instance-property dimensions which now also supports interaction with variable number of representations, e.g., AutoSF.

Follow up:
I think it makes sense to change the generic type of ERModel[HeadRepresentation, RelationRepresentation, TailRepresentation] to ERModel[EntityRepresentation, RelationRepresentation] and only distinguish in the interaction.

[cthoyt]

Do you think this interface is private enough that changing it won't have an impact? I guess it should be implicitly covererd by existing tests. If so,

[mberr]

Do you think this interface is private enough that changing it won't have an impact? I guess it should be implicitly covererd by existing tests. If so,

I tend to say yes 😅 If someone depends on an exact API, version pinning is still possible.