Add support for JSON format for in_ and exclude_ filters values

[Natim]

Historically in_ and exclude_ filters are comma separated only.

When we introduced contains_ and contains_any_ we decided to support JSON objects.

I think we should backport the logic to in_ and exclude_ or at least supports it for arrays of strings.

[Natim]

Refs https://github.com/Kinto/kinto-http.py/issues/187

[glasserc]

I spent a little while trying to track down the history here. I think it's just an oversight. The main issue with supporting JSON values was in the storage code rather than the query deserialization code -- see https://github.com/Kinto/kinto/pull/1258. Then, when contains_ and contains_any_ were added in https://github.com/Kinto/kinto/pull/1604, but the behavior of in_ and exclude_ was left as-is. The code right now:

https://github.com/Kinto/kinto/blob/593abdbc15c358590c799b8d86461563da8efbe2/kinto/core/resource/schema.py#L231-L247

This aaaalmost works. A JSON array like ["a","b","c"] gets split into ["a", "b", and "c"]. Then we deserialize each element, but since the first and third aren't JSON, only the middle one gets deserialized correctly. That's why the strange behavior @Natim saw in his bug report.

The existing behavior can remain as a fallback AFAICT. We should just try native_value first.