WIP: Moves the vulnerabilities list to the dashboard app

What does this MR do?

This adds the first class vulnerabilities list to the group, project, and instance security dashboards.

It's behind the feature flag first_class_vulnerabilties.

When the feature flag is turned on, it should render first class vulnerabilties in the dashboard lists, instead of the usual vulnerability findings.

NOTE: This is experimental/alpha. Turning on the feature flag will break the filtering, and make some of the dashboard widgets make very little sense. This is intended at this stage.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (see #204847 (closed))
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Touches #207373 (closed)