Kubernetes to Helm migration path

[michaellzc]

Provide high-level guidance for customers currently running kustomize-based or pure kubectl deployments to migrate to helm.

Out of scope:

• Creation of any automated tooling to simplify migration
• Helm chart support prior to Sourcegraph version 3.39

[github-actions]

Heads up @dan-mckean @caugustus-sourcegraph @kevinwojo @michaellzc - the "team/delivery" label was applied to this issue.

[virginiaulrich]

And one more for the product backlog to decide how we want to approach this so the work is defined/agreed upon etc @dan-mckean

[michaellzc]

There's some weird permission issue with codeinsights-db after migration from root kustomize to non-root helm

How to reproduce?

• kubectl-apply-all.sh in deploy-sourcegraph
• apply migrate-nonroot overlay
• apply non-root overlay
• apply the kustomize+helm thing we have for dogfood