Problem/Motivation
The base class \Drupal\layout_builder\Plugin\Layout\MultiWidthLayoutBase allows layout plugins to define different width options.
Whichever option is listed first becomes the default value.
This is not clear when implementing the method, and should be made both explicit and customizable.
Proposed resolution
Move the current "first option is default" implementation to a new protected method and allow subclasses to provide their own implementation.
Remaining tasks
User interface changes
N/A
API changes
Non-breaking API addition (protected method in base class with provided implementation).
Data model changes
N/A
Release notes snippet
N/A