Remove tezos-bake-monitor-lib dependency

Clarification and motivation

We depend on this library. In short, it adds some extra maintenance burden. Specifically:

1. It's not quite stable, so sometimes we have to update it. And Tezos itself is unstable, so it increases instability. We have to fix something there a few times.
2. It's not on Hackage, so morley does not build on Hackage.
3. Packages depending on morley have to add this library to extra-deps.

Apparently, we only use it to implement conversion of Michelson stuff to JSON. I think it's not a big problem to implement proper JSON encoding ourselves. Then maintaining our code probably won't be harder than maintaining this dependency.

Acceptance criteria

1. Investigate how much work we should do to stop depending on tezos-bake-monitor-lib.
2. If that's not too much, do that work and remove tezos-bake-monitor-lib from the dependencies.