Issue #2095399 by Berdir: Merge DatabaseStorageController and DatabaseStorageControllerNG.

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

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

...b/Drupal/Core/Entity/EntityStorageControllerInterface.php

...Drupal/Core/Entity/FieldableDatabaseStorageController.php

...upal/Core/Entity/FieldableEntityStorageControllerBase.php

core/lib/Drupal/Core/Entity/Query/Sql/Tables.php

...ggregator/lib/Drupal/aggregator/FeedStorageController.php

...ggregator/lib/Drupal/aggregator/ItemStorageController.php

.../lib/Drupal/custom_block/CustomBlockStorageController.php

...s/comment/lib/Drupal/comment/CommentStorageController.php

core/modules/contact/lib/Drupal/contact/Entity/Message.php

...tact/lib/Drupal/contact/Tests/Views/ContactFieldsTest.php

.../content_translation/Tests/ContentTranslationTestBase.php

...ugin/field/field_type/ConfigurableEntityReferenceItem.php

...Drupal/entity_reference/Tests/EntityReferenceItemTest.php

core/modules/field/field.install

core/modules/field/field.views.inc

...dules/field/lib/Drupal/field/Plugin/views/field/Field.php

core/modules/field/lib/Drupal/field/Tests/BulkDeleteTest.php

...odules/field/lib/Drupal/field/Tests/Views/ApiDataTest.php