Feat(Q): Add Group AmazonQ availability settings

• 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 adds the AmazonQ availability settings for the Group Settings page.

• It takes over where the Duo settings would normally be. It looks like in a recent MR, these Duo settings have moved. We'll keep the Amazon settings here for now and open a follow-up to figure out what to do in the long run with UX.
• When the availability is turned off, we remove the Amazon Q service account user from any subgroups or projects.

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	Screenshot
demo_group_settings

How to set up and validate locally

Prerequisites:

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.

Instructions for these changes:

1. Visit a group and go to Settings
2. EXPECTATION: A section for Amazon Q should be in the group settings page.
3. Try changing the Availability and click Save changes.
4. EXPECTATION: A toast message should pop up that this was successful.
5. Add the service account user for Amazon Q to the group and a subproject.
6. Go to the group's Settings and under the Amazon Q section set the availability to Always Off.
7. Click Save changes.
8. EXPECTATION: The service account user should have been removed from the group and subproject.