Add exec-profile arguments to eks update-kubeconfig

[Nevon]

Issue #, if available: #9759

Description of changes: Adds --exec-profile argument to eks update-kubeconfig. When set, this profile will be set as AWS_PROFILE within the generated kubeconfig. This allows for using one profile (the session profile) to generate the config, without requiring that same profile for connecting to the cluster or for assuming the --role-arn.

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I was unable to find any documentation on how to set up this repository for local development, so I'm not sure that my added unit test actually passes. We shall see what the CI says.