UPDATE or BUG/SMALL - Structure of JSON response data doesn't match documentation

# Description

While updating the documentation on the [structure of the JSON response data](https://lookit.readthedocs.io/en/develop/researchers-experiment-data.html#structure-of-json-response-data) to add the new 'eligibility' field, I noticed that there are some discrepancies between the the documentation and data download structure. Specifically, in the data downloads:
- The `exp_data` object has been moved out of the `response` key and is now a top-level key
- There is a top-level `consent` key that is not listed in the docs
- There is no `global_event_timings` key (at least, not in the response data sets that I have downloaded)
- The `response` object contains additional keys that are missing from the docs: `date_created`, `withdrawn`, `parent_feedback`, `birthday_difference`, `video_privacy`, `databrary`

I can fix some of these discrepancies when I update the response data documentation (https://github.com/lookit/lookit-docs/issues/364) but we should probably compare the data downloads and docs more closely for discrepancies, and check whether any differences are due to bugs in the data downloads (rather than just a failure to update the docs).

# Screenshots

Here's the structure of a recent data download (for comparison with the structure outlined in the [docs](https://lookit.readthedocs.io/en/develop/researchers-experiment-data.html#structure-of-json-response-data) ):


Start by comparing the data-download structure shown in the issue with the “Structure of JSON response data” section in the linked documentation and the updates planned in lookit-docs#364. Confirm which discrepancies reflect documentation omissions and which indicate download bugs; done means the discrepancies are resolved or clearly documented with the appropriate follow-up.

Written by the indexing model from the issue text.