Dast modal UX improvement

What does this MR do?

This Merge Request solves: #229524 (closed)

• It solves the problem that the DAST Modal does close on the click of the Download Button

This Merge Request does not solve the Issue that the wait between the click event and the start of the Users download can be rather long on large projects. This issue is being discussed here

If you are trying to reproduce this issue on gitlab.com or locally I have created a repo which has everything to reproduce set up. jannik_lehmann/dast-test-project!1 (closed)

Demo Video

dast-modal-version-4

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