Draft: Migrate vulnerability state dropdown to GlDisclosureDropdown

What does this MR do and why?

Migrate vulnerability state dropdown to GlDisclosureDropdown

Migrates the vulnerability state dropdown to a GlDisclosureDropdown component. The flyout dismissal reason dropdown has been migrated away from Popper.js in favor of Floating UI.

Changelog: changed
EE: true

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Run yarn as this currently runs a dev build of @gitlab/ui.
2. Navigate to a project's vulnerability details page, e.g. http://gdk.test:3000/gitlab-org/gitlab-shell/-/security/vulnerabilities/88
3. Change the vulnerability's status.

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 #418099 (closed)