Issue #2236553 by xjm, dags, Gaelan, alexpott: Config import validation needs to be able to list multiple issues and the messages should be translatable.

Wrong commit credit.

This reverts commit 0a93d9a1.

Issue #2124535 by Berdir, alexpott, Désiré, xjm | yched: Prevent secondary configuration creates and deletes from breaking the ConfigImporter.

Issue #1808248 by alexpott, beejeebus, tayzlor, Nitesh Sethia: Add a separate module install/uninstall step to the config import process.

Issue #2224873 by alexpott: Handle a config entity with the same name but different UUID being imported.

Issue #2218003 by tim.plunkett: ConfigImporter assumes that a ConfigEntity uses a storage controller that implements ConfigStorageControllerInterface.

Issue #2098119 by beejeebus, alexpott, chx: Replace config context system with baked-in locale support and single-event based overrides.

Issue #2133325 by mtift, alexpott, sun: Create a site UUID on install and only allow config sync between sites with the same UUID.

Issue #2130811 by alexpott, Gábor Hojtsy, vijaycs85, sun, Wim Leers: Use config schema in saving and validating configuration form to ensure data is consistent and correct.

Issue #2066535 by tim.plunkett, jsst, Berdir: Add EntityManagerInterface and stop typehinting with EntityManager.

Issue #1969572 by neclimdul, larowlan, hussainweb, dawehner, damiankloip, ParisLiakos, pwieck, Berdir, socketwench: Make Uuid a service.

Issue #1890784 by alexpott, YesCT, heyrocker, tim.plunkett, EllaTheHarpy, beejeebus: Refactor configuration import and sync functions.