Component config entity should validate that the SDC actually (still) exists

Actually, the Component config entity already handles this, largely. So we don't need all that infrastructure.

But we're missing some validation here.

@f.mazeikis ran into this problem while working on 📌 Auto-create/update Component config entities for all discovered SDCs that meet XB's minimum criteria Fixed , and this validation would have caught it. So, prioritizing this.

This blocks #3470550 — see #3470550-16: Component config entities are incomplete: missing entries for optional props, causing errors in ComponentPropsForm → .

https://git.drupalcode.org/project/experience_builder/-/merge_requests/2... solved this as part of 📌 Component config entity should validate that the SDC actually (still) exists Active .