Issue #1911728 by ParisLiakos, Xano, dawehner, jibran, David_Rothstein: Remove hook_init().

core/authorize.php

core/core.services.yml

core/includes/common.inc

...b/Drupal/Core/EventSubscriber/LegacyRequestSubscriber.php

...al/Core/EventSubscriber/SlaveDatabaseIgnoreSubscriber.php

...les/action/tests/action_loop_test/action_loop_test.module

...modules/language/tests/language_test/language_test.module

.../lib/Drupal/overlay/EventSubscriber/OverlaySubscriber.php

core/modules/overlay/overlay.module

core/modules/overlay/overlay.services.yml

.../Drupal/system/Tests/System/IgnoreSlaveSubscriberTest.php

...rupal/system/Tests/Theme/ThemeEarlyInitializationTest.php

core/modules/system/system.api.php

core/modules/system/system.module

core/modules/system/tests/modules/menu_test/menu_test.module

...dules/system/tests/modules/system_test/system_test.module

...Drupal/theme_test/EventSubscriber/ThemeTestSubscriber.php

...modules/system/tests/modules/theme_test/theme_test.module

...s/system/tests/modules/theme_test/theme_test.services.yml

core/modules/update/update.module