Cardano Updates

Changelog for `cardano-node-10.7`

Add cabal-gild as part of the pre-commit hook in our Nix devShell.

Wow so much type hell, was catching missing instances for half a day, note to
self: try not to mess with instance decls

Added the following tests:

* JSON roundtrip property test
* Unit test for trying to decode an empty object `{}` for the
  `NonEmptyMap`, and an empty list `[]` for the `NonEmptySet`. These
  scenarios are expected to fail with a specific error message.

Using `pre-commit run --all-files` will now run `fourmolu`,
`cabal-gild`, `shellcheck` and `nixpkgs-fmt` on all modified files.

Did not add `hlint` for now because there are *lots* of warnings that
will take time to fix.

Currently, the `B` constructor contains a `ByteString` (pinned in
memory) with a max length of 64 bytes. Since the `ByteString` is small
and can be instantiated frequently, it makes more sense to use an
unpinned byte array representation (`Data.Array.Byte.ByteArray`) so
that we can take advantage of Haskell's garbage collection to improve
memory allocation of objects in the heap.

We also place an upper bound on `nothunks` because of new orphan
instance (`instance NoThunks ByteArray`) that is going to be upstreamed.