Deterministic genesis generation

[adlrocha]

Background

Initially we were planning to store the genesis.car for the subnet actor to make it available for new peers joining the network, but this CAR is ~12MiB on average, which may be too big to store it on-chain. As a workaround we can store the genesis template for the subnet and all peers can deterministically generate the genesis.car from the template (1-2 MiB).

Implementation.

This PR:

• Modifies the genesis implementation to include a deterministic genesis creation mode.
• It provides a new IPC endpoint that agents can use to generate a template for their subnet from which they can generate the genesis.car for the subnet.

Future work

• Persist the genesis in IPFS and add the cid of the subnet genesis in the subnet actor
• Populate the subnet name into the genesis template (we don't know a-priori the subnetID until the actor has been deployed).