Add the REST config to the Ingress guides

[conceptualshark]

Description

Relates to #4137
This addresses:

• adding the Zeebe REST API configuration into the Ingress guides
• adding a note that the ingress path should match the context path to the (pre-8.7 combined) Ingress guides
• linking to the ingress config, clarify the context path is for Zeebe Gateway, and update organization of the context path section in the Zeebe REST API overview

I've added these changes to the available documentation, back through 8.5 for the Ingress docs - prior to that the formatting changes.

I've added these options into /next assuming that if the /v1 APIs remain available, it will still be useful, and if they're removed, we can address removing it at the same time as any other updates, but let me know if this isn't the right call.

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).

• My changes require an Engineering review, and I've assigned the Engineering DRI or delegate.
• My changes require a technical writer review, and I've assigned @camunda/tech-writers as a reviewer.

[github-actions]

👋 🤖 ✅ Looks like the changes were ported across versions, nice job! 🎉

You can read more about the versioning within our docs in our documentation guidelines.

[pepopowitz]

makes sense to me, and clarifies. Thank you!