Problem/Motivation
Other modules will need to store things alongside the Layout Builder defaults.
For example, the UI proposed in #2946227: Provide ability to alter blocks presented in ChooseBlockController.
As a core patch it can add it's own methods to section storage, but as a contrib module it currently has no access.
Proposed resolution
DefaultsSectionStorageInterface should extend ThirdPartySettingsInterface
Remaining tasks
N/A
User interface changes
N/A
API changes
API addition to experimental @internal code
Data model changes
N/A, any additions to third party settings are responsible for their own schema additions