Upgrade to Helm v4

[zerok]

Since this is a major release, it will require a bit of evaluation and prep-work from our side to make sure that we don't accidentally break workflows. Perhaps we could even somehow support v3 and v4 and let the users choose which version they want to use?

[strowi]

FYI: Testing tk-0.36.1 with helm-v4 produces at least an error syncing charts from oci:

~> tk tool charts vendor
~> tk tool charts vendor --log-level debug
{"level":"info","time":"2025-11-20T09:29:37+01:00","message":"Vendoring..."}
{"level":"info","time":"2025-11-20T09:29:37+01:00","message":"Syncing Repositories ..."}
{"level":"debug","argv":["repo","update","--repository-config","/tmp/charts-repos691619330"],"time":"2025-11-20T09:29:37+01:00","message":"running helm"}
Error: Error: failed to update the following repositories: [oci://quay.io/strimzi-helm]

while working fine with helm-3.19.1.

[zerok]

Thank you for testing! I wonder if we will have to support both versions at least for a certain time window.