feat(info): add --labels flag to print label statistics

[mikix]

With chart-review info --labels, you'll get a table summarizing how often each label was used by each annotator, plus a unioned view of how often each label was used by any annotator.

I Also took out the little list of labels printed with just bare info since it felt redundant and let me simplify that view a bit. Not committed to this stance, but it felt cleaner to me.

I've reviewed with Andy about some of the more "what would a researcher want to see?" choices here - like the "union" Any-annotator section and using the final grouped labels instead of the intermediate labels.

Checklist

• [x] Consider if documentation (like in docs/) needs to be updated
• [x] Consider if tests should be added

[mikix]

Just pushed a quick update to sort the list of annotator names, FYI.

Will land this and then release 1.2.0 I think