Add further region "Outer Page" to place blocks directly inside the body

Problem/Motivation

If you have absolutely positioned blocks like we have on https://www.drupal.org/project/cookies, there is no good region on Olivero to place them. The footer region, for example, has a relative position, so the block position origin is the footer, not the body.

Steps to reproduce

Proposed resolution

Add a new region "Outside", "Outside Page", "Body", ... ? which will be printed as a direct child of the body element.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet