✨ Add separate eks kubeconfig secret keys for the cluster-autoscaler

[cnmcavoy]

What type of PR is this? /kind feature

What this PR does / why we need it: Cluster Autoscaler can not mount and consume the Cluster API Kubeconfig because the secret contents are refreshed every ten minutes, and no API Machinery exists to reload a kubeconfig safely.

Initially, I attempted solve this in the Cluster Autoscaler: https://github.com/kubernetes/autoscaler/issues/4784 - However meeting with SIG APIMachinery on Nov 1 2023, the SIG cautioned against this approach and advised splitting the token out from the kubeconfig, as there is existing machinery to reload a token file auth. By switching to this approach, no change in the Cluster Autoscaler is needed, users only need to update their Cluster Autoscaler configuration to use the correct secret file from their secret volume mount.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #4607

Special notes for your reviewer:

Checklist:

• [X] squashed commits
• [X] includes documentation
• [X] adds unit tests
• [ ] adds or updates e2e tests

Release note:

Add separate eks kubeconfig secret keys for the cluster-autoscaler to support refreshing the token automatically, see eks kubeconfig for more info.