F3 topdown: certificates syncing & verification (PoC)

[LePremierHomme]

Create PoC for syncing finalized tipsets from an F3 node.

• Retrieve the chain of finality certificates and power table diffs, starting from genesis.
• Use either libp2p or RPC endpoints
• Pipe the data into a verifier module for verification. The actual verification code verifier can be partially mocked for now

This ticket creates a Rust library to match the functionality already built in Golang

• https://github.com/ChainSafe/rust-f3
• Implement BDN signature aggregation scheme ChainSafe/rust-f3#34

[linear]

IPC-196 F3 topdown: certificate syncing & verification (PoC)

[phutchins]

Potentially could split this up into syncing certificates and separately verification