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### Proposed changes

This PR exposes the helm template `--kube-version` argument so it can be manually specified in situations when there is no access to the Kubernetes API server (e.g running a diff in CSA mode with no connection to the cluster).

Prior to this merge:
* If there were zero k8s contexts --> this field was unset meaning helm would default to some old version (1.20.0 at the time of writing) if it couldn't connect to the k8s context
* 1+ k8s contexts --> would always try to contact the API server to get the version leading to an error if the API server was unreachable.

This variable will override the behavior in either case, but is mostly useful in the first case or when the context in the second case is malformed / unreachable. 

### Related issues (optional)

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Closes pulumi#2563