Refactor the removal of repeated commitments in Shplemini + Better structure in Flavors' entities

[iakovenkos]

Currently, we are erasing elements see this PR in the vectors of commitments and scalars in ShpleminiVerifier. That's expensive in general. Need to introduce better getters in Flavors to compute the correct linear combinations of scalars multilplying the same commitment. Introduce better structure in Entities.

For some reason, I got stuck with the ECCVM trying to improve this, i.e. I changed the loop processing shifted commitments and scalars in the first place, it worked with Ultra and Mega(ZK), but the verification kept failing for ECCVM.