feat(boojum): Add a flag to control which prover to use at diamond init

[mm-zk]

What ❔

• depending on the CONTRACTS_PROVER_AT_GENESIS environment variable, set correct VkHashes

Why ❔

• later migrations of provers, happen via migration mechanism, but for boojnet and local setups, we need a way to set the prover that will be used at genesis.
• otherwise, we'd have to run the 'old' prover to prove at least one block (to do the migration).

Comments

Change is backwards compatible - if flag is not set, we'll use the old (current) setup