Implement chunking for C2a and C2b proving

[0xjei]

Parent: #1736

Scope

Track the implementation of chunked proving for C2a and C2b. The implementation is currently in progress in PR #1772.

Completion criteria

• Complete and review the chunked C2 implementation.
• Confirm that chunked proofs preserve the existing C2 public inputs, commitments, and verification flow.
• Add or update the required tests and benchmarks.
• Validate the implementation with the active LBFV configuration.

Related work

• PR: feat: add chunked C2 proving [skip-line-limit] #1772

[0xjei]

• align with main
• double-check @zahrajavar findings
• double-check design & functioning
• final internal & coderabbit reviews
• merge in an experimental branch for lbfv that must stay aligned with main