[MR Widget Eng] Code quality
This issue is to track the engineering efforts of the Code quality widget using the new [Merge request reports framework](https://design.gitlab.com/regions/merge-request-reports).

### Resources
- [Related UX Issue](https://gitlab.com/gitlab-org/gitlab/-/issues/336178)
- [Figma Design Specifications](https://www.figma.com/file/qEddyqCrI7kPSBjGmwkZzQ/Component-library?node-id=40483%3A44585)
- [Merge request reports framework](https://design.gitlab.com/regions/merge-request-reports)
### Implementation Plan
- Get first Iteration of this Widget with what is currently available merged. https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82113
The following things need to be adjusted but are independent from each other so the order in which they are worked on doesn't matter.
**Request optimization:**
- [Implement dedicated API endpoint for collapsed/uncollapsed state](https://gitlab.com/gitlab-org/gitlab/-/issues/355390)
**Subtext Support:**
- [[MR Widget Core Extension] Subtext is only supporting plain text, should support links](https://gitlab.com/gitlab-org/gitlab/-/issues/354495)
- [Implement Subtext for Code Quality MR Widget Extension](https://gitlab.com/gitlab-org/gitlab/-/issues/355581)
**Severity Icon Naming**
- [add Severity Icon to Server Response](https://gitlab.com/gitlab-org/gitlab/-/issues/355714)
epic