Issue #2274517 by Wim Leers: Remove \Drupal\Core\Field\PrepareCacheInterface.

core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php

core/lib/Drupal/Core/Field/PrepareCacheInterface.php

...ules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php

core/modules/field/src/Tests/FieldAttachStorageTest.php

...odules/field_test/src/Plugin/Field/FieldType/TestItem.php

.../modules/text/src/Plugin/Field/FieldType/TextItemBase.php

core/modules/text/src/Tests/TextWithSummaryItemTest.php

core/modules/text/text.module