Issue #3245376 by phenaproxima, tedbow: Move the path locator entirely to Package Manager

automatic_updates.services.yml

src/PathLocator.php

src/Validation/ReadinessValidationManager.php

src/Validator/DiskSpaceValidator.php

src/Validator/WritableFileSystemValidator.php

tests/src/Functional/FileSystemOperationsTest.php

.../Kernel/ReadinessValidation/CoreComposerValidatorTest.php

...src/Kernel/ReadinessValidation/DiskSpaceValidatorTest.php

...l/ReadinessValidation/WritableFileSystemValidatorTest.php

tests/src/Kernel/UpdaterTest.php