[Variant][Compute] Add batch processing for Variant-JSON String conversion

[harshmotw-db]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

We should add functionality to allow users to parse batches of JSON strings to batches of variants and vice versa. This way, unless the user explicitly wants low-level control, they do not need to deal with concepts such as VariantBuilder.

Describe the solution you'd like

We should implement two new functions batch_json_string_to_variant and batch_variant_to_json_string in a new crate called parquet-variant-compute which work with batches of JSON Strings and Variants as input and outputs.

Describe alternatives you've considered

Additional context

#7783 (comment)

[Samyak2]

@harshmotw-db are you working on this currently? Asking because I see that this issue is not assigned yet and I wanted to pick it up if it wasn't

[harshmotw-db]

@Samyak2 Yeah, I do have a PR in the works. I'll assign you to review

[alamb]

label_issue.py automatically added labels {'parquet'} from #7783