log the payload when data collection is disabled, for QA purposes

[rhelmer]

Checklist for reviewer:

• The description should reference a bug or github issue, if relevant.
• There must be a CHANGELOG.md entry for any non-test change.
• Any change to the NPM commands must be carefully reviewed to make sure it won't break the Add-ons pipeline.
• Any version increase must follow the release process.

[rhelmer]

@Dexterp37 I am finding it very difficult to QA studies that haven't been released yet, what do you think about doing this?

Happy to consider alternatives but I'd like to make it as easy as we can for folks doing this sort of testing. If we're concerned about potential leakage I could see dumping the encrypted payload instead but this would be pretty difficult for all but the most sophisticated test user :)

[Dexterp37]

I think this is very reasonable! Please add a changelog entry :)