Add solution html to vulnerability modal

What does this MR do and why?

Related #452483 (closed)

In %17.0 we added the solutionHtml to PipelineSecurityReportFindingType with !149583 (merged).

Now we're using this to display the GitLab flavored markdown solution in the vulnerability modal.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Prerequisites

1. You need an EE license
2. You need to have runners enabled (See $2408961 for setting up a runner)
3. Import https://gitlab.com/lorenzvanherwaarden/test-remediations-with-solution-html (❗ different than default security-reports repo)
4. Run a pipeline on master

Validate

1. Go to the latest pipeline > security tab
2. Click the critical finding to open the finding modal
3. Validate that the modal's Solution part contains the markdown, including a rendered mermaid diagram and the green addition label.