Docs guidelines: Combine "Product availability details" and "Document product versions"

The Product availability details page includes everything about the DETAILS block.

The Document product versions page includes information about:

• The history block
• How to deprecate/remove a page/content

I think the information about the DETAILS block and history block should go on the same page? Or be more clearly related.

Then the information about deprecating content can be its own page.

(Side note, we're starting to get a huge proliferation of pages under Contribute to documentation and should maybe think about how to better organize them.)

(Another side note, I wonder if we should show a history on the Documenting experimental and beta features page. It's not clear to me what language to use when something changes from Beta to GA, for example, but I think we have this information here.)

This issue is to review this information and see if we can organize it better. It's grown over time and could use some attention, I think.