atp, http, qemu: complete Json.t/Json.Codec.Value.t disambiguation
- hermest main.ml: generate dune.inc with [libraries atp json] (not jsont).
- Json.to_string/of_string args: codec is Json.Codec.Value.t (not Json.t
which is a type).
- test_huri: Json.to_string_exn/of_string_exn raise; remove bogus
pattern-match on result.
- Various value-context uses of Json.t fixed to Json.Codec.Value.t when
they were codec args, and to Json.string/Json.null etc. when they were
value constructors.