6 files declare their use of Merge in Zircon Profile 8

DatabaseStorage.php in core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php

Contains \Drupal\Core\KeyValueStore\DatabaseStorage.

DatabaseStorageExpirable.php in core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php

Contains \Drupal\Core\KeyValueStore\DatabaseStorageExpirable.

Merge.php in core/lib/Drupal/Core/Database/Driver/sqlite/Merge.php

Contains \Drupal\Core\Database\Driver\sqlite\Merge.

Merge.php in core/lib/Drupal/Core/Database/Driver/pgsql/Merge.php

Contains \Drupal\Core\Database\Driver\pgsql\Merge.

Merge.php in core/lib/Drupal/Core/Database/Driver/mysql/Merge.php

Contains \Drupal\Core\Database\Driver\mysql\Merge.

MergeTest.php in core/modules/system/src/Tests/Database/MergeTest.php

Contains \Drupal\system\Tests\Database\MergeTest.