Issue #2089671 by disasm, tim.plunkett: Convert non-test form callbacks to new form controller.

core/modules/book/book.module

core/modules/book/book.pages.inc

core/modules/book/book.routing.yml

core/modules/book/book.services.yml

...lib/Drupal/book/Access/BookNodeIsRemovableAccessCheck.php

core/modules/book/lib/Drupal/book/Form/BookForm.php

core/modules/content_translation/content_translation.module

...modules/content_translation/content_translation.pages.inc

...ranslation/Access/ContentTranslationManageAccessCheck.php

...rupal/content_translation/Form/ContentTranslationForm.php

...translation/Routing/ContentTranslationRouteSubscriber.php

core/modules/language/language.admin.inc

core/modules/language/language.module

core/modules/language/language.routing.yml

...odules/language/lib/Drupal/language/Form/LanguageForm.php

core/modules/locale/lib/Drupal/locale/Form/LocaleForm.php

core/modules/locale/locale.bulk.inc

core/modules/locale/locale.module

core/modules/locale/locale.pages.inc

core/modules/locale/locale.routing.yml