Jobs to be done experiment in first mile -- asking for objective [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/285566

This is an experiment that asks registering users why they're signing up for gitlab.

Screenshots (strongly suggested)

[pending]

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because it's an experiment.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content