feat: add zk proof generated by risc0 for state transition in lean consensus

[DimitriosMitsios]

Introducing zk proofs to lean consensus

The goal of this PR is to allow the block proposer to generate a zk proof of the state transition function. The proof will be gossiped and other validators will be able to verify it. We will use risc0 zkVM.

To-Do

• Create a cli flag proof_gen
• Add proof_gen to LeanNodeConfig
• Create LeanProverServiceMessage enum with GenerateBlockProof variant
• Add new field proof_gen: bool to struct ValidatorService
• Set up guest environment and generate a proof
• Implement proof triggering (every 200 slots)
• Implement proof gossiping via new block_proof topic
• Gossip and validate the proof (implemented but not tested)