[hotshot-state-prover] proof generation

[mrain]

closes: #1985

I tried but cannot make functions generics because of the StakeTable trait bounds. It's too complicated.

The tests are not implemented yet for srs problem. I'm handling it now.

[mrain]

This PR is ready for view. cc @alxiong @chancharles92

1. padding is done in the circuit building function to avoid more memory copies.
2. It's hard to make proof generation function generic. There are too many trait bounds. Although, this is really tempting to me.
3. Only minimal test for proof generation, many bad cases are checked inside the circuit building tests.
4. Other cleanup tasks will be handled during integration (e.g. struct alignment with consensus implementation)

[alxiong]

👍 good work!

Apart from concrete comments, I'd like to see better/clearer organization of bad path in circuit tests.
e.g. let bit_masked_sig = |sigs| { .. } could be an internal lambda function, and can summarize some helper function to make the test code reads more smoothly.

^^ just my opinion, improve at @mrain's discretion.

[alxiong]

we need to change block_comm name as it is wrong, (both in this PR and in types/traits/state.rs

suggestions:

• block_comms_root
• block_comm_history_root

[alxiong]

LGTM! 🚀