Assume Role to find EKS cluster for config update

[5nafu]

Issue #, if available: #8554

Description of changes:

This PR will assume a given role when trying to update the kubeconfig.

While aws eks update-kubeconfig --role-arn... would add the required parameters to the user section of the configfile, but will fail finding the cluster if the original profile does not have access. This PR will fix the issue and assume the role before getting the cluster description.

[djtung]

Hi, I'm on the team working on EKS at AWS. As I understand:

1. The current documentation specifies that --role-arn is meant for "cluster authentication" (kubectl connection), not for the AWS CLI's cluster discovery process.
2. This fix overloads the --role-arn parameter by using it for both:
   • AWS CLI cluster discovery
   • Kubernetes cluster authentication
3. This change would be breaking for existing customers who may have tools/scripts relying on the current documented behaviour

Better would be to implement the suggestions from here, perhaps with the latter of providing another parameter so that the two roles can be clearly separated. If you're willing to make that change for adding a new parameter (and update the documentation), we'd be happy to approve it.

[sdomme]

HI @djtung, thank you very much for your feedback. We reworked this contribution in #9443 in favour to your suggestions. We confirmed with @5nafu, that this PR is superseded by the new request.
Please have a look. Thnaks