dhi: refresh how-to use

[craig-osterhout]

Description

Pending #24616 as it may cause conflicts.

• Merged the use in k8 topic into the general use topic.
• Removed the generic dhi differences table and just xref'd to the migrations topic that also has it.
• Simplified the pull & run section down to just explaining the different registries.
• Added how to use els variants and removed that standalone topic.
• Replaced dev multi-stage example with an xref to the migration topics
• Added DD auth for k8 example for local dev

Related issues or tickets

ENGDOCS-3222
ENGDOCS-3226

Reviews

• Editorial review

[netlify]

✅ Deploy Preview for docsdocker ready!

Name	Link
🔨 Latest commit	ed3edf2
🔍 Latest deploy log	https://app.netlify.com/projects/docsdocker/deploys/69d532b3852fc2000871f0a6
😎 Deploy Preview	https://deploy-preview-24629--docsdocker.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 project configuration.