use protobuf content type instead of json for k8s client

[bhavi-koduru]

What type of PR is this?

Which issue does this PR fix:

What does this PR do / Why do we need it:

This MR is a part of effort to elevate single eks cluster performance by migrating the EKS components to use protobuf instead of json.

Modify kubeconfig type to use content type application/vnd.kubernetes.protobuf instead of json for performance gain.

If an issue # is not available please add steps to reproduce and the controller logs:

Testing done on this change:

Automation added to e2e:

Will this PR introduce any new dependencies?:

Will this break upgrades or downgrades. Has updating a running cluster been tested?:

Does this PR introduce any user-facing change?:

No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.