Add proof verification to relay

[thedevbirb]

Closes #28.
This PR introduces the same verification functionality created in https://github.com/chainbound/bolt/pull/11/files#diff-d37e00b1a7a3229e87982a7e48cf2a9f37eb80688297501e95edd50250ee2ea8R335-R409 in the relay. In particular, the check is executed while saving the submit block request on Redis, because the block is converted to a bid which includes the transactions_root needed for verification.

NOTE: at the moment this PR doesn't include an e2e test of the endpoint for the following reasons:

• the endpoint handler logic is particularly complex to test as whole; in fact at the time of writing the upstream repository doesn't include such test (reference but split its converage into smaller units
• the verification logic has been extensively tested in the mev-boost PR and with prior work