19 files declare their use of ViewEntityInterface in Drupal 8

AddHandler.php in core/modules/views_ui/src/Form/Ajax/AddHandler.php

ConfigHandler.php in core/modules/views_ui/src/Form/Ajax/ConfigHandler.php

ConfigHandlerExtra.php in core/modules/views_ui/src/Form/Ajax/ConfigHandlerExtra.php

ConfigHandlerGroup.php in core/modules/views_ui/src/Form/Ajax/ConfigHandlerGroup.php

datetime_range.module in core/modules/datetime_range/datetime_range.module

Field hooks to implement a datetime field that stores a start and end date.

dblog.module in core/modules/dblog/dblog.module

System monitoring and logging for administrators.

Display.php in core/modules/views_ui/src/Form/Ajax/Display.php

Rearrange.php in core/modules/views_ui/src/Form/Ajax/Rearrange.php

rest.module in core/modules/rest/rest.module

RESTful web services module.

SqlTest.php in core/modules/views/tests/src/Unit/Plugin/query/SqlTest.php

View.php in core/modules/views/src/Entity/View.php

views.module in core/modules/views/views.module

Primarily Drupal hooks and global API functions to manipulate views.

ViewsEntitySchemaSubscriber.php in core/modules/views/src/EventSubscriber/ViewsEntitySchemaSubscriber.php

ViewsFormBase.php in core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php

ViewsFormInterface.php in core/modules/views_ui/src/Form/Ajax/ViewsFormInterface.php

ViewsModerationStateFilterTest.php in core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php

ViewsUIController.php in core/modules/views_ui/src/Controller/ViewsUIController.php

views_test_data.module in core/modules/views/tests/modules/views_test_data/views_test_data.module

Helper module for Views tests.

ViewUI.php in core/modules/views_ui/src/ViewUI.php