Epic: Lotus integration

[Kubuxu]

Acceptance criteria:

• F3 runs within lotus using its libp2p stack
• Messages are propagated through pubsub
• Finality exchange over libp2p streams
• Lotus feeds chain information into F3
• F3 has a way to bootstrap

(WIP)

### Tasks
- [ ] https://github.com/filecoin-project/go-f3/issues/103
- [ ] https://github.com/filecoin-project/go-f3/issues/15
- [ ] #225
- [ ] https://github.com/filecoin-project/go-f3/issues/270
- [ ] https://github.com/filecoin-project/go-f3/issues/271
- [ ] https://github.com/filecoin-project/go-f3/issues/272
- [ ] https://github.com/filecoin-project/go-f3/issues/365

[jennijuju]

@Kubuxu question for you - how would the application fetch the finality / get a signal from lotus that "we have reached finality for this epoch via 3"? Something new along with ChainHead (which only gives your the latest block w/o confirming it is finalized) ?

[Kubuxu]

I haven't thought about it a lot, but it seems reasonable, ChainGetFinalizedHead or something like that.

[Kubuxu]

PR in lotus: https://github.com/filecoin-project/lotus/pull/12119 I aim to make it ready for review before Monday. I would appreciate reviews on Monday there.