feat(ivc): accumulation of step circuit instances

[cyphersnake]

Motivation
Practically complete realization of task #316

Overview
Impl of accumulation of step circuit instances

• Addition of a step_circuit_instances_hash_accumulator to the RelaxedPlonkInstance structure.
• Implementation of methods to fold and conditionally select step circuit instances.
• Modification of existing methods to incorporate the new accumulator.
• Update to testing modules to cover the changes.

[cyphersnake]

I plan to finalize the documentation, as well as add a test to nifs mod with an instance column in the last, finalizing #316 the next PR