Resolve "Show DAST results in the MR widget"

What does this MR do?

Shows DAST results in the MR widget.

Frontend

• Fetch dast report
• Add dast report in mr widget
• Find a way to show desc and solution UX
• Stripe <p> tags from json output
• Add tests
• Create an issue to handle the technical debt added in here: https://gitlab.com/gitlab-org/gitlab-ee/issues/4455
• Port stripHtml to CE

Are there points in the code the reviewer needs to double check?

no

Why was this MR needed?

So a user can see results of dynamic scanning in MR widget.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan

What are the relevant issue numbers?

Closes #4348 (closed). Part of https://gitlab.com/gitlab-org/gitlab-ee/issues/3956