Cardano Updates

- Improve type safety by linking request and response type for each
  rpc method (Morpho.RPC.Abstract.RpcMethod)
- Abstract over RPC upstreams (Morpho.RPC.Abstract.RpcUpstream), which
  will allow running the morpho node with a mocking RPC upstream without
  having to mock an HTTP server
- As part of the above, network manager objects are now reused between
  requests
- As part of the above, clean up tracing of RPC calls. Now each RPC call
  is traced in a single location (Morpho.RPC.Tracing), and specifically not
  in the main Morpho.Node.Run module
- As part of the above, move http exception handling (and all other
  json-rpc specific bits) into the Morpho.RPC.JsonRpc module
- Remove the previous mock Pow chain (Morpho.RPC.PoWMock), which was only
  used by the tests. Above changes enable a much nicer testing interface
- Split the RPC protocol and encoding into a separate module
  (Morpho.RPC.JsonRpcProtocol), making sure to not reuse any ToJSON
  implementations from morpho's data types, so as to have a fixed protocol
  that doesn't change with different underlying data types

Since unusedPowBlockRef always just stored at most one element, changing
it from a `Map PowBlockRef [Node]` to a `Maybe (PowBlockRef, [Node])`.
Also renaming it to `currentCandidate` which is more accurate.

Other minor simplifications

Documents parts of the code

Before this change whether a vote is valid was checked twice:
- Once by first getting the ledger state, then checking if there's
  a duplicate vote already and if it's at the correct interval
- Once again with tryAddTxs, which actually inserts the vote, but this
  time with a more up-to-date ledger state, but the exact same checks
  for duplicate votes and the correct interval are performed again there
  (via applyTx)

(And actually a third time when the block is forged, but we can't avoid
this)

This change removes this duplication and as a result cleanly splits
errors during vote creating and vote application

This relies on the corresponding change on the mantis side

Simplifies tracing a lot by:
- Not using toObject for showing log events and instead just using their
  Show instance.
- Removing the counting forge tracers, they don't seem that
  useful. Can be readded later if needed
- Remove the special mempool tracer because it also doesn't seem very
  useful and can be readded later if needed