[FEA] Add a json_tuple kernel

[revans2]

Is your feature request related to a problem? Please describe.
We support get_json_object, which is great, and we have implemented json_tuple in terms of get_json_object. But this is problematic because we have to run get_json_object multiple times. Once for each column we want to pull out. It would be much better if we just had a kernel that could do multiple columns at the same time, and it would not need to worry about the complexity of JSON PATH as it is just looking for top level columns.