Export requirements as a CSV

What does this MR do?

Frontend for #290813 (closed)

Testing and verifying

• Open rails console

• Enable the feature flag: Feature.enable(:requirements) and Feature.enable(:import_requirements_csv)

• Debugging: If requirements are not getting exported try restarting rails background jobs: gdk restart rails-background-jobs

• Resolve issues with rails background jobs: !47064 (comment 465179958)

to see the email

• Tail the rails background job logs: gdk tail rails-background-jobs
• Export from the UI and wait a couple of seconds and find this line in the console.

• And, then open it in the browser. 🤙

Known Bug

• The export count is incorrect when filters are applied

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team