EKS event centralization and discoverability only works from management account within AWS Organization

The event centralization and discoverability pattern in `observability/eks-event-centralization-discoverability` works only from the management account of an AWS Organization, which is not consistent with best practice. Preferred strategy would be to:

* Deploy solution to a non-management, central tooling account (instead of relying on a management account)
* Using targeted cross-account roles instead of relying on the general purpose `OrganizationAccountAccessRole`
* Using CDK and CloudFormation StackSets to simplify deployment and ensure that new accounts and new EKS clusters within these accounts are discovered and handled correctly

Start in observability/eks-event-centralization-discoverability and trace how deployment currently depends on the management account and OrganizationAccountAccessRole. Define and implement a deployment approach for a non-management tooling account with targeted roles and CDK/CloudFormation StackSets; done means new accounts and EKS clusters are discovered and handled correctly.

Written by the indexing model from the issue text.