[ENHANCEMENT] Add ability to create datasets from jsonl files

[szeitlin]

Is your feature request related to a problem? Please describe.
We have 'golden' datasets with input + expected output in json formats. It's extra work to have to reformat to CSV.
Would be great if we didn't have to do a lot of transformations to migrate from another eval tool.

Describe the solution you'd like
The ability to directly use files formatted with {'input': [], 'expected_output': []} as json, or if there are several rows like that, jsonl

Describe alternatives you've considered
It seems like we have to write some code to handle reformatting for the time being.