Integrate with Ctools context plugins

Problem/Motivation

Integrates ctools context plugins and relationships as part of #3299868: [meta] Context plugin system.

[ctools plugins] added relationships. We need to let page_manager know how to use them. There are many forms that need a tweak and in a few places where page_manager gets context, we needed it to also get relationships.

Also, Layout Builder and Page Manager don't play nice together when it comes to context. When you select a context in Page Manager it doesn't show up in Layout Builder as fulfilling what block plugins needed to be placed until you went through a forceable save because it wasn't consulting the tempstore that was already there. That would mean that users would have to hit save mid edit before the system would be functional. This patch attempts to resolve those issues by bringing the temp stores more in line with each other.

Remaining tasks

• Upgrade path