Issue #2423241 by Mile23: Merge ConfigurablePluginCollectionTest into DefaultLazyPluginCollectionTest

Revert "Issue #1986330 by subhojit777, marcelodornelas, wheatpenny, kasperg, timaholt, stefank, AkshayKalose, develCuy, valthebald, moymilo, YesCT, dawehner, tstoeckler: When Batch ID doesn't exist, Drupal should emit a 404"

Somehow broke testbot/HEAD. Reverting for now.

This reverts commit 30432a03.

Issue #1986330 by subhojit777, marcelodornelas, wheatpenny, kasperg, timaholt, stefank, AkshayKalose, develCuy, valthebald, moymilo, YesCT, dawehner, tstoeckler: When Batch ID doesn't exist, Drupal should emit a 404

Issue #2423579 by mpdonadio, xjm, heilop, Wim Leers, webchick: Url::fromUrl('user-path:/') should throw an exception when a path component without a slash is given

Issue #2388627 by JeroenT, filijonka, ultimateAnkit, tadityar, rpayanm, adci_contributor: Remove usages of drupal_is_front_page

Issue #2414255 by lauriii, Jeff Burnz, dawehner, davidhernandez: Subtheme template inheritance working in reverse order

Issue #2419065 by jhedstrom: Switching the entity storage class should not be considered a definition update that requires schema changes

Issue #2051467 by jhedstrom, dawehner, amateescu, Berdir, herom, Mile23: Expand and convert to phpunit tests for \Drupal\Component\Transliteration

Issue #2338727 by znerol, almaudoh: Replace static SessionManager::$enabled property with WriteSafeSessionHandler class and resolve hidden circular dependency between SessionManager and SessionHandler

Issue #2417647 by Wim Leers, effulgentsia: Add leading slash to paths within 'user-path:' URIs, to allow 'user-path:' URIs to point to the <none> route

Issue #2363099 by Gábor Hojtsy, Berdir, swentel, plach: Using translated field definition descriptions in entity schema results in different schema definitions, resulting in update.php changes

Issue #2418613 by pwolanin: Fix #0 bug in toUriString() method in Url class, clarify toString() vs toUriString()

Issue #552478 by markcarver, sun, effulgentsia, jhedstrom, ohnobinki: Restrict "self-closing" tags to only void elements in drupal_pre_render_html_tag

Issue #2418139 by pwolanin, kgoel, dawehner, almaudoh, Wim Leers: Add a toUriString method to Url class and add a route: scheme

Issue #2030607 by hussainweb, Mile23, Kingdutch, alexpott, balagan, amateescu, adci_contributor, Xano, mon_franco, cilefen: Expand EntityDisplayBase with methods

Issue #2050759 by tim.plunkett, fietserwin: Move drupal_chmod and other code in file.inc to a Drupal\Core\File\FileSystem class

Issue #2417793 by effulgentsia, Wim Leers, YesCT, yched, dawehner: Allow entity: URIs to be entered in link fields

Issue #2417333 by Wim Leers, pwolanin, xjm, dawehner: Add support for user-path: scheme to Url class

Issue #2412509 by kgoel, pwolanin, Wim Leers, larowlan, effulgentsia, dawehner, xjm: Change LinkItem.uri to type 'uri' rather than 'string' and introduce user-path: scheme

Issue #2364157 by mpdonadio, dawehner, martin107, Berdir, pcambra, naveenvalecha, tim.plunkett: Replace most existing _url calls with Url objects