Display fixed findings

What does this MR do and why?

So far we missed displaying the fixed findings. This MR adds that functionality.

Screenshots or screen recordings

Before:

After:

How to set up and validate locally

1. Fork https://gitlab.com/gitlab-examples/security/security-reports/
2. Enable feature flag: refactor_security_extension
3. Create an MR
4. Go the MR page and scroll the reports.

You should see a list of added and fixed reports. You can verify we display the right findings by looking at response of the security_reports endpoint API calls.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #397688 (closed)