Issue #3295791 by Theresa.Grannum, tedbow: Add return types where needed

...c_updates_extensions/tests/src/Build/ModuleUpdateTest.php

...dates_extensions/tests/src/Functional/UpdaterFormTest.php

...er_test_validation/src/EventSubscriber/TestSubscriber.php

src/BatchProcessor.php

...omatic_updates_test/src/StagedDatabaseUpdateValidator.php

.../AutomaticUpdatesTestDisableValidatorsServiceProvider.php

tests/src/Build/CoreUpdateTest.php

tests/src/Functional/AutomaticUpdatesFunctionalTestBase.php

tests/src/Functional/UpdaterFormTest.php

tests/src/Kernel/ProjectInfoTest.php

tests/src/Kernel/ReleaseChooserTest.php

tests/src/Unit/LegacyVersionUtilityTest.php