Support cache GC feature via controller flags

[terrytangyuan]

Summary

Several community members have started using this feature via experiment variables CACHE_GC_PERIOD and CACHE_GC_AFTER_NOT_HIT_DURATION. They want to know when this feature will be mature.

Let's use this issue to collect feedback on this feature and improve when necessary before we move them to controller flags instead of environment variables. This is part of https://github.com/argoproj/argo-workflows/issues/8608.

If you are using this feature, please upvote and provide any feedback.

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[alexec]

I’m actually not a fan of the config-map. It is quite expensive to add new items to it. It’s not amenable to Kustomize patches so not GitOps friendly. I would continue to use env vars for unstructured config.