Issue #2392293 by bircher, tim.plunkett, alexpott, cilefen, gobinathm: Refactor hook_system_info_alter implementations to use ModuleUninstallValidatorInterface

Issue #2444231 by Wim Leers, nlisgo: Fix CacheableInterface so it makes sense (was: "Make Config objects & Entities implement CacheableInterface + add BubbleableMetadata::createFromCacheableObject()")

Issue #2432837 by Wim Leers, Fabianx: Make cache contexts hierarchical (e.g. 'user' is more specific than 'user.roles')

Issue #2429261 by Wim Leers: Replace the hardcoded cache key on the book navigation block with a 'book navigation' cache context

Issue #2209025 by dawehner, fgm, pwolanin: Phase 3 - Make the BookManager interface more coherent, move more code out of book.module.

Issue #2109035 by tim.plunkett, damiankloip, dawehner, chx: Make access checkers (much) easier to find.

Issue #2048223 by dawehner, ParisLiakos, herom, fubhy, damiankloip, vijaycs85, joelpittet, tim.plunkett: Add $account argument to AccessCheckInterface::access() method and use the current_user() service.

Issue #2099095 by jibran, tim.plunkett: Create BreadcrumbBuilderBase and remove the boilerplate code from BreadcrumbBuilders.

Issue #2070651 by pwolanin, dawehner, larowlan, tim.plunkett, ParisLiakos: Introduce a path-based breadcrumb builder, remove the one that's based on {menu_links()}.

Issue #1938316 by disasm, jaskho, stella, scor, tim.plunkett, jibran | Crell: Convert book_outline() to a new-style Controller.

Issue #1938314 by kgoel, mparker17, Kars-T, disasm, tim.plunkett, daffodil_naveen, ygerasimov, jibran, dawehner, wamilton, Letharion | Crell: Convert book_export() to a new-style Controller.

Issue #2057869 by dawehner, jibran: Provide an alias for 'plugin.manager.entity' called 'entity.manager'.

Issue #1498674 by plach, das-peter, Schnitzel, dawehner, YesCT, attiks, Berdir, Gábor Hojtsy, Soul88, Carsten Müller: Refactor node properties to multilingual.

Issue #1938296 by disasm, YesCT: Convert book_admin_overview() and book_render() to a new-style Controller.