Re-implement Helm Tests

[nfuden]

[jenshu]

We used to generate a go struct for helm values, that we would use in tests to validate the structure of the helm values we passed in (and also used for docs). That code has been removed now. It would be good to add it (or a replacement) back that we can use in helm tests.

Depends on the "helm gen" parts of #10528

[timflannagan]

See https://github.com/solo-io/gloo/tree/main/install/test when picking this up. We should audit/consider those test cases when re-implementing this work.

[github-actions]

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