Convert tests to use JSON-XOP

[t-b]

This 1 is much more powerful than the undocumented JSONSimple operation.

[t-b]

For IP6 I'm attaching a custom JSON XOP version with all tests passing, built from 00468445 of branch compile-for-ip6 (internal repo).

[t-b]

JSON-XOP-Inofficial-IP6-Version.zip

[t-b]

It probably makes sense to first switch from Json_Simple to the JSON XOP using IP8/9, create an MR, merge it. And then get the tests passing with IP6.