Deprecate explicit data sharing in favor of survey questions and versioning

[gino-m]

I would propose another simpler solution:

• Solve [Project] Prevent changes to survey from making data inaccessible  #1701 and [Data consistency] Introduce versioning / changelog of survey tasks? #2221
• Remove data sharing agreements altogether and let the organizer implement them as a question in the survey.
• Changes to the question will be logged/tracked because of [Data consistency] Introduce versioning / changelog of survey tasks? #2221.

@kenstershiro @lecrabe for approval.

Originally posted by @gino-m in #2178

This change would only apply to new surveys; existing surveys would continue to work as-is.