DOC-967 Add more details to the node upgrade doc for Kubernetes

[JakeSCahill]

Description

Review deadline: 25 Jan

We recently had a P1 related to ephemeral data loss due to how Azure handles automated node upgrades. We already implemented a clarification in docs to recommend disabling automated node upgrades: https://redpandadata.atlassian.net/browse/DOC-875

However, @chrisseto and I met and discussed improvements we can make to the node upgrade guide, including:

• Make sure to disable the Decommission/NodeWatcher controllers before upgrading to avoid them interfering with the manual steps.
• Provide step-by-step instructions for the network-backed PV and ephemeral storage cases.

Page previews

https://deploy-preview-960--redpanda-docs-preview.netlify.app/current/upgrade/k-upgrade-kubernetes/

Checks

• New feature
• Content gap
• Support Follow-up
• Small fix (typos, links, copyedits, etc)

[netlify]

✅ Deploy Preview for redpanda-docs-preview ready!

Name	Link
🔨 Latest commit	3feb92d
🔍 Latest deploy log	https://app.netlify.com/sites/redpanda-docs-preview/deploys/67a097031593620008ff2cec
😎 Deploy Preview	https://deploy-preview-960--redpanda-docs-preview.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[Feediver1]

Love the flow chart--very helpful!
One thing...
I'm not a designer, but the layout here feels a bit off.
Not sure I understand why the legend appears aligned with the diagram. I would expect it to site above it.
Then, the Start circle and everything underneath would be center-aligned underneath. This would leave a lot less blank space here. Thoughts on having borders around these diagrams?

[Feediver1]

Please have a look at comment re diagram. Otherwise, well-written!

[chrisseto]

Sorry for taking so long on this one. IIRC this ask was kicked off as we were trying to determine how best to migrate an Azure cluster as we had written up some instructions. That operation ended up going the worst way imaginable which got me thinking more deeply about this topic, especially because the landscape of self hosted is much broader than cloud.

Here's a heavily annotated flow chart that should capture most cases. It doesn't touch on how to perform the operation manually, just whether or not it needs to be manual 😓