Create Poll#makeDelayedRequest Method and Implement on Security Dashboard/Vulnerabilities

What does this MR do?

This merge requests adds a Poll#makeDelayedRequest(delay) method for the polling, so that you can delay the initial request by a variable amount of time in milliseconds.

That method is also implemented in the footer.vue of the vulnerability security page. See the discussion about it.

Screenshots

The discussions request starts the notes request through polling but it is delayed by 6 seconds (which it wasn't before).

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

Closes #217184 (closed)