Feat(Q): Identity provider info and FE for AmazonQ admin

• 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 sets up the FE for the Amazon Q admin settings. It also adds the IdentityProviderPayloadFactory which is used to pull information needed to register an Amazon identity provider.

Screenshots or screen recordings

When not connected	When connected

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. For now, you'll need to ensure that CLOUD_CONNECTOR_SELF_SIGN_TOKENS=1 is set.

Instructions for these changes:

1. Enable the feature flag amazon_q_integration with Feature.enable(:amazon_q_integration) in a rails console
2. Visit Admin > Settings > General and look for GitLab Duo with Amazon Q section. Click View configuration setup.
3. Review that the page loaded with no errors.

To test this view for when Amazon is connected:

1. Start a rails console with rails c.

2. Update the Ai::Settings.instance record with something like (2 is just an arbitrary user ID):

   Ai::Setting.instance.update(amazon_q_role_arn: 'test-arn', amazon_q_service_account_user_id: 2, amazon_q_ready: true)

Please note: It's expected that the FE buttons don't work right now. This is behind a feature flag and the functionality will be included in a future MR. See parent MR for more context.