Use predefined values for site-sections in Prismic rather than tags

[davidpmccormick]

What?

We're in the process of replacing /pages/ with whichever site-section a page has been tagged with in Prismic (#11248).

In the future, if we change our site-sections, this would require a migration to also update the associated tags.

A more future-proof to consider moving towards might be updating Prismic document content models to include a linked SiteSection where the vocabulary is controlled, and if an item is edited, that edit will automatically propagate to all necessary pages without requiring a migration.

Why?

Maintainability

[rcantin-w]

I'm still into this idea but we'll have to see if we can still use a filter here to get the correct page Route: #11283