[helm] feat: support preheat function in kraken-proxy

[fbuchmeier-abi]

Hi folks,

I've enabled the kraken-proxy server required for preheat (e.g. with Harbor) on port 81.

Also, I've added the option to override the allowed_cidrs from the helm values, this can be useful when using EKS with the VPC CNI, where requests to kraken are not comming from localhost but from the hosts private IP address.

In addition to this, I've updated the kubeVersion restriction to work with current kubernetes versions. See also https://github.com/uber/kraken/issues/277

Best regards, Florian.

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