Issue #3318313 by kunal.sachdev, tedbow: Make OverwriteExistingPackagesValidatorTest fixture-less

...existing_validation/active/vendor/composer/installed.json

..._existing_validation/active/vendor/composer/installed.php

...validation/staged/modules/module_1/module_1.info.yml.hide

...validation/staged/modules/module_2/module_2.info.yml.hide

...validation/staged/modules/module_3/module_3.info.yml.hide

...le_5_different_path/module_5_different_path.info.yml.hide

...existing_validation/staged/vendor/composer/installed.json

..._existing_validation/staged/vendor/composer/installed.php

...sts/src/Kernel/OverwriteExistingPackagesValidatorTest.php