[EKS] [feature]: Private marketplace for *custom* EKS addons

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**Tell us about your request**
I want to be able to build my own container image and bring it for use as an addon within the EKS service, ideally requiring its use on all clusters.

**Which service(s) is this request for?**
This could be Fargate, ECS, EKS.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
If we build our own security tooling, have monitoring tools or literally anything that is not provided as a native addon there is no easy way to enforce its installation on all clusters.

The issue names no repository files, tests, or entry points to inspect. Start by clarifying the intended EKS, ECS, or Fargate scope and the enforcement requirements; done would mean a defined way to use a custom container image as an addon across clusters.

Written by the indexing model from the issue text.