BETA5 paperfruits

Ordered list of papercuts / low-hanging fruit for BETA5: look for the RELEASE in Adélie Linux / Adélie Package Tree label.

Other tasks:

• "should" "must" release new adelie/horizon and update adelie/packages to include the fix for adelie/horizon#372 (closed), but not required because adelie-infra/automedia uses horizon from git to build images, but horizon-as-packaged is what installs the system.
• "should" release new adelie/gcompat and update adelie/packages, but maybe this is a post-release action. I have a ton of fun stress tests for gcompat planned, and want to set aside time to file issues and work on those improvements for future releases. Not urgent.

Please update/comment as necessary. This is a live issue.