Allow synthetic component definitions for BC sake

Overview

At present we're using component IDs in code that assume there's a matching config entity with a matching ID pattern

This means for BC layers we need to have every component defined that is already in use.
This will prevent people using LB/PG from evaluating XB.

Proposed resolution

Wait for 📌 Decorate the SDC plugin manager and allow components defined in code Active and 📌 Support complex SDC prop shapes: introduce (Storable)PropShape to compute field type storage settings Fixed , then adapt the code in https://git.drupalcode.org/project/experience_builder/-/merge_requests/68 to allow layout builder BC layer to define components on the fly.

User interface changes