Verify watchtower's longest chain proofs in risc0

[ekrembal]

Issue Description

Continuation of #496

After verifying watchtower's winternitz signatures, we should verify the groth16 proofs of header chain proofs.

Tasks

Parts of the task:

• Generate a header chain proof. See: https://github.com/chainwayxyz/risc0-to-bitvm2, the header chain, get help from @ozankaymak
• Sign the header chain proof with winternitz signature
• Verify the groth16 proof inside risc0 guest, along with verifying winternitz signatures

Deadline of the Issue

Thursday