9 files declare their use of MigrateFieldPluginManagerInterface in Drupal 8

FieldDiscovery.php in core/modules/migrate_drupal/src/FieldDiscovery.php

FieldDiscoveryTest.php in core/modules/migrate_drupal/tests/src/Unit/FieldDiscoveryTest.php

FieldDiscoveryTest.php in core/modules/migrate_drupal/tests/src/Kernel/d7/FieldDiscoveryTest.php

FieldDiscoveryTestClass.php in core/modules/migrate_drupal/tests/modules/field_discovery_test/src/FieldDiscoveryTestClass.php

FieldType.php in core/modules/field/src/Plugin/migrate/process/FieldType.php

MigrationState.php in core/modules/migrate_drupal/src/MigrationState.php

MigrationStateUnitTest.php in core/modules/migrate_drupal/tests/src/Unit/MigrationStateUnitTest.php

ProcessField.php in core/modules/field/src/Plugin/migrate/process/ProcessField.php

ProcessFieldTest.php in core/modules/field/tests/src/Unit/Plugin/migrate/process/ProcessFieldTest.php