Problem/Motivation
Since #2951242: Allow BaseFieldDefinition::setInitialValueFromField() to set a default value - this fixes issues with block_content_update_8400(), it is possible that a database field schema specification to have both initial and initial_from_field set, which means that two update queries will be executed to set the initial value when the field is added to the table.
Proposed resolution
Change the execution order so only one update query is performed.
Remaining tasks
Review.
User interface changes
Nope.
API changes
Nope.
Data model changes
Nope.