Issue #2686207 by Berdir: Convert simpletest kernel tests in modules A-I to phpunit

core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php

...dules/aggregator/tests/src/Kernel/AggregatorTitleTest.php

...odules/aggregator/tests/src/Kernel/FeedValidationTest.php

...dules/aggregator/tests/src/Kernel/ItemWithoutFeedTest.php

.../modules/block/tests/src/Kernel/BlockConfigSchemaTest.php

core/modules/block/tests/src/Kernel/BlockInterfaceTest.php

core/modules/block/tests/src/Kernel/BlockStorageUnitTest.php

core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php

core/modules/book/tests/src/Kernel/BookUninstallTest.php

...s/breakpoint/tests/src/Kernel/BreakpointDiscoveryTest.php

...or/tests/modules/src/Kernel/CKEditorPluginManagerTest.php

...odules/ckeditor/tests/modules/src/Kernel/CKEditorTest.php

...tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php

...dules/comment/tests/src/Kernel/CommentFieldAccessTest.php

.../comment/tests/src/Kernel/CommentStringIdEntitiesTest.php

...odules/comment/tests/src/Kernel/CommentValidationTest.php

...odules/config/src/Tests/AssertConfigEntityImportTrait.php

core/modules/contact/tests/src/Kernel/MessageEntityTest.php

...n/tests/src/Kernel/ContentTranslationConfigImportTest.php

...on/tests/src/Kernel/ContentTranslationSettingsApiTest.php