1201 make risc0 public input optional

[PatStiles]

closes #1201

To Test:

• Run local testnet
• Submit risc0 proofs to the local batcher via make batcher_send_risc0_burst. Observe they are processed.
• Submit risc0 proof with empty public inputs to the local batcher via make batcher_send_risc0_task_no_pub_input. Observe they are processed.