Issue #3230510 by phenaproxima, tedbow: Turn ExclusionsTest into a functional test

automatic_updates.services.yml

src/Event/ExcludedPathsSubscriber.php

tests/fixtures/fake-site/files/private/ignore.txt

tests/fixtures/fake-site/files/public/ignore.txt

tests/fixtures/fake-site/files/staged.txt

tests/fixtures/fake-site/sites/default/services.yml

tests/fixtures/fake-site/sites/default/settings.local.php

tests/fixtures/fake-site/sites/default/settings.php

tests/fixtures/fake-site/sites/default/staged.txt

tests/fixtures/fake-site/sites/simpletest/ignore.txt

..._updates_test/src/AutomaticUpdatesTestServiceProvider.php

tests/modules/automatic_updates_test/src/TestUpdater.php

tests/src/Functional/ExclusionsTest.php