Remove coupling from group by feature flag

What does this MR do and why?

Remove coupling from group by feature flag

When :group_level_vulnerability_report_grouping is disabled we were not able to display the enhanced filtering because it was tightly coupled. These changes remove that coupling.

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

How to set up and validate locally

1. Make sure :group_level_vulnerability_report_grouping feature flag is disabled.
2. Make sure :vulnerability_report_enhanced_filtering feature flag is enabled.
3. Visit the Project Level Vulnerability Report.

The filters should appear as follows:

4. Visit the Group Level Vulnerability Report.

The filters should appear as follows: