Replace SCALE with borsh entirely

[kayabaNerve]

I'm unsure this is feasible technically/feasible within our timeline.

It'd simplify the protocol though.

[kayabaNerve]

This is completely infeasible.

If #647 occurs, we can define our own merklization scheme for events, and manually implement Encode/Decode on Event, Transaction, Block s.t. borsh is used internally. This should completely remove scale from the blockchain itself. Caveats apply as the RPC would be scale (#625 relevant) and consensus commits would presumably be. I honestly care less about consensus as we'll ideally replace it eventually, and at that point, we can checkpoint the last block produced under the old consensus after the transition.