Improve consistency of "Geo proxying for secondary sites"

Problem to solve

Right now, the Geo proxying for secondary sites document needs some attention. I have identified a few problems:

1. We link to a separate page for URL configuration that I think can simply be merged into this page
2. The nomenclature is inconsistent
   1. For instance, the Set up a unified URL for Geo sites and Geo proxying with Separate URLs should use more similar phrasing
3. There's room for expansion of existing content to add detail for customers, and add new content for other configurations (like sticky round-robin DNS when they don't need location-aware DNS)
4. The page would benefit from an overall content and clarity review

Further details

Proposal

To solve the outlined problems, I'd like to create a separate MR for each of the following:

1. Lift-and-shift content from Location-aware public URL into Geo proxying for secondary sites and set up a redirect from the old page
2. Edit the content of Geo proxying for secondary sites to resolve outlined issues above
3. Eventually remove the redirect from the old page

Who can address the issue

I'm happy to serve as DRI for this issue and do most of the work. I'll work with @axil for TW purposes and the Geo team for content purposes. Since this proposal is hefty, I wanted to discuss it on an issue first, before I assign time to working on the changes.

Other links/references