Consolidate configuration sections in docs

[alamb]

Which issue does this PR close?

• Part of [Epic] Better / Improved Documentation, Tutorials and Examples #7013

Rationale for this change

The main navbar on the left of the page is already pretty big. I noticed that there are two pages for config settings

I looked and https://datafusion.apache.org/user-guide/runtime_configs.html has only a single setting:

Let's consolidate the pages into a single page

What changes are included in this PR?

1. Consolidate generation script to make a single page
2. Add a redirect from the old page to the new page
3. Remove old page and generation scrpt

Are these changes tested?

I tested this manually - that the doc looks good locally and that the redirect works

Are there any user-facing changes?

[comphead]

thanks @alamb nice cleanup