Foundations for Cloud Seed AWS integration

What does this MR do and why?

• Introduces feature flag cloudseed_aws
• Introduces policy rule admin_project_aws such that only project maintainers (and above) can manage AWS configuration
• Adds a placeholder nav-item under Project :: Infrastructure for AWS (as seen in the screenshot). Only visible when the feature flag is active and the user meets the policy rule (i.e. is maintainer or owner for the project)

Screenshots or screen recordings

How to set up and validate locally

1. Enable cloudseed_aws feature flag on local instance
2. Navigate to any project where you are maintainer+
3. Infra nav-item should render AWS sub nav-item

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.