[istio]: add helmfile

[alebabai]

what

implement istio helmfile

why

closes #45

known issues

helm delete --purge istio fails to delete all resources; subsequent install or upgrade fails.

Upgrading cloudposse-incubator/istio
Release "istio" does not exist. Installing it now.
Error: customresourcedefinitions.apiextensions.k8s.io "gateways.networking.istio.io" already exists

Workaround:

kubectl get customresourcedefinition  -n istio-system | grep 'istio'|awk '{print $1}'|xargs kubectl delete customresourcedefinition  -n istio-system

references

• Helm delete does not clean the custom resource definitions istio/istio#7688

[osterman]

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