Problem/Motivation
Follow up from #2933924: Move \Drupal\field_ui\Form\EntityViewDisplayEditForm::getFieldLabelOptions() to a trait post from there
\Drupal\field_ui\Form\EntityViewDisplayEditForm::getFieldLabelOptions() contains code that is essential to configuring a field formatter, with 4 magic keys, yet it is in a protected method on a single form implementation.
Steps to reproduce
TBD
Proposed resolution
make the allowed values into constants
Remaining tasks
TBD
User interface changes
TBD
API changes
TBD
Data model changes
TBD