[PP-1] Validate that content templates are attached to entity bundles that fulfill XB's requirements

Overview

Postponed on 📌 Allow XB to be used on all node types Active .

The ContentTemplate config entity is attached to a specific entity type, bundle, and view mode. At the moment, we only require that the bundle exist at all, but we don't check that the bundle is actually usable by XB. We should validate that, but it'll have to happen once the blocker is in.

Proposed resolution

TBD

User interface changes

TBD