Feat(Q): Admin disconnect FE

• Feature branch: DRAFT: Amazon q spike (!174614 - closed)
• Side note: This was originally developed in a private fork by GitLab team members in collaboration with Amazon's team.

What does this MR do and why?

This MR implements the FE for Add Amazon Q disconnect endpoint (!176082 - merged) and goes beyond just upstreaming the feature branch changes by implementing the designs in https://gitlab.com/gitlab-com/ops-sub-department/aws-gitlab-ai-integration/integration-motion-planning/-/issues/232+.

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

Demo	After (connected)	Modal	Success
demo_disconnect

How to set up and validate locally

1. You'll need to make sure you have an Ultimate license and AI features setup on your GDK. See these instructions.
2. Setup the AmazonQ configuration following these instructions. Make sure that the availability is set to On by default.

To test the changes in this MR:

1. Visit the instance's Amazon Q settings in Admin > Settings. Under the GitLab Duo with Amazon Q section click View configuration setup.
2. EXPECTATION: With the Amazon Q integration connected, a Remove button should be visible next to the ARN field.
3. Click Remove.
4. EXPECTATION: Removing the Amazon Q integration should be successful.