Issue #2808329 by quietone, phenaproxima: Add default values to Row constructor

.../tests/src/Unit/Plugin/migrate/process/d6/FileUriTest.php

.../tests/src/Kernel/Plugin/migrate/process/FilterIdTest.php

core/modules/migrate/src/Row.php

...migrate/tests/src/Kernel/MigrateEntityContentBaseTest.php

...modules/migrate/tests/src/Kernel/process/CopyFileTest.php

.../modules/migrate/tests/src/Unit/MigrateExecutableTest.php

core/modules/migrate/tests/src/Unit/MigrateSourceTest.php

...Unit/Plugin/migrate/destination/EntityContentBaseTest.php

core/modules/migrate/tests/src/Unit/RowTest.php

...migrate/tests/src/Unit/destination/EntityRevisionTest.php

...ts/src/Unit/destination/PerComponentEntityDisplayTest.php

...rc/Unit/destination/PerComponentEntityFormDisplayTest.php

core/modules/migrate/tests/src/Unit/process/IteratorTest.php

.../modules/migrate/tests/src/Unit/process/UrlEncodeTest.php