feat(commitments-api): Bolt RPC component

This issue is to track responsibilities and specs for the Bolt RPC component.

Bolt RPC is an optional proxy to route commitment requests from users to the correct proposer in the lookahead
On top of being great for improving the UX, it also sits in the perfect spot to fulfil the role of "challenger agent"

Here is a brief outline of the implementation steps necessary for what outlined above:

[ ] rpc: build a simple proxy server to forward requests from users to proposers
[ ] rpc: integrate with the Bolt registry to know to which proposer requests should be forwarded.
[ ] rpc: figure out how we the ip advertisement / discovery should work (related to #47)
[ ] challenge: add a signing backend able to send transactions for proving faults
[ ] challenge: add listener component to track all pending commitment challenges and detect liveness & safety faults
[ ] challenge: add simulation component to simulate challenge games locally before sending transactions onchain
[ ] challenge: add challenge tracking component to keep an updated view of pending & resolved dispute games

chainbound / bolt