Change record status: 
Project: 
Introduced in branch: 
8.x
Description: 

To avoid confusion with the field config entity, \Drupal\Core\Entity\Field\Field has been renamed to \Drupal\Core\Field\FieldItemList.

The following subclasses and interfaces have been renamed accordingly.
Drupal\Core\Entity\Field\Field --> \Drupal\Core\Field\FieldItemList
Drupal\Core\Entity\Field\FieldInterface --> \Drupal\Core\Field\FieldItemListInterface
\Drupal\file\Plugin\field\field_type\FileField --> \Drupal\file\Plugin\Field\FieldType\FileFieldItemList

Impacts: 
Module developers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done