Problem/Motivation
When accessing Layout Builder overrides via REST (i.e. when accessing an overridden entity's layout field), the contents of sections appear empty.
Proposed resolution
We should add a normalizer for the layout_section DataType, which ensures that sections can be properly serialized and unserialized via the serialization API (and REST).
Remaining tasks
Write a patch, possibly discuss what setting (unserializing) sections looks like via an API like REST.
User interface changes
None.
API changes
A new normalizer will be added for the layout_section DataType.
Data model changes
None.