Resolve "Show results from docker image scan in the merge request widget"

What does this MR do?

Shows result of CI scan on docker image

Frontend

• Adds support to fetch clair report
• Parses and stores received data
• Adds support in collapsible section to render text information
• Adds support in issue component to render an extra type
• Adds tests to all changed components & store, for success and error cases.

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

no

Why was this MR needed?

To integrate container static analysis into MR widget. First step in https://gitlab.com/gitlab-org/gitlab-ee/issues/3724

Screenshots (if relevant)

|loading|error|no vulnerabilities|vulnerabilities| |--|--|--|--|--|--| |||||

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3781
• 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 #4249 (closed)