Issue #2512866 by lauriii, Berdir, Wim Leers, Fabianx, effulgentsia, catch, dawehner: CacheContextsManager::optimizeTokens() optimizes ['user', 'user.permissions'] to ['user'] without adding cache tags to invalidate that when the user's roles are modified

Issue #2468151 by lhangea, rpayanm, Palashvijay4O: Rename the CacheContexts service to CacheContextsManager

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

Issue #2433599 by Wim Leers: Ensure every (non-views) pager automatically associates a matching cache context