Revert "Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system."

This reverts commit fc04601c.

Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Issue #1798296 by damiankloip, Xano, David_Rothstein, Crell, dawehner: Integrate CSRF link token directly into routing system.

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

Issue #1943846 by fubhy, effulgentsia, tim.plunkett: Improve ParamConverterManager and developer experience for ParamConverters.

Issue #1890878 by corvus_ch, ygerasimov, berenddeboer, Crell, fubhy the cat, effulgentsia: Add modular authentication system, including Http Basic; deprecate global .

Issue #1988508 by katbailey: Stop pretending we support Symfony bundles when we really just have service providers.

Issue #1947536 by andypost, donquixote, larowlan, splatio, kim.pepper, alexpott, Crell, tim.plunkett: Convert drupal_get_breadcrumb() and drupal_set_breadcrumb() to a service.

Issue #1813762 by ParisLiakos, Jose Reyero, YesCT, japicoder, attiks: Introduce unified interfaces, use dependency injection for interface translation.

Issue #2003578 followup by chx: twig_cache() must be FALSE in install.php registerTwig because we don't know if files folder is writable yet.

Issue #2003578 by Jon Pugh, joelpittet: Fixed twig_cache() must be FALSE in install.php registerTwig because we don't know if files folder is writable yet.

Issue #1957042 by Kevin Morse, foopang, xjm, Fabianx, Cottser: Document why a method in CoreBundle is public static

Revert "Issue #1938980 by Crell, rootatwc, tim.plunkett: Move controller derivation to route enhancers."

Temporary rollback; this broke AJAX paths. Working on better test coverage.

This reverts commit 221099b5.

Issue #512026 by Berdir, effulgentsia, sun, marcingy, Eric_A, xjm, katbailey, Damien Tournoud, alexpott, beejeebus, pillarsdotnet: Move () storage from cache to new state/key-value system.

Issue #1664844 by alexpott, cweagans, heyrocker, eojthebrave, ACF, Berdir: Convert image toolkits into plugins.

Issue #1764474 by Berdir, chx, alexpott, pounard, msonnabaum: Make Cache interface and backends use the DIC.

Issue #1547008 by Berdir, Sutharsan: Replace Update's cache system with the (expirable) key value store.

Issue #1209226 by catch, Berdir, miro_dietiker, beejeebus, dagmar: Fixed Avoid slow query for path alias whitelists.

Issue #1843220 by mkadin, dawehner, Crell, effulgentsia, Wim Leers: Convert form AJAX to new AJAX API.

Issue #1845402 by Crell, amateescu, dawehner, klausi, g.oechsler: Change notice: Update menu link access checks for new router.

Issue #1891980 by Berdir, amateescu: Add Service termination API to reliable terminate/shut down services in the container.

Issue #1929136 by Gábor Hojtsy, alexpott, YesCT: Fixed override-free context, move global config overrides back to an event listener.

Issue #1836008 by dawehner, Berdir, alexpott, katbailey, effulgentsia, EclipseGc: Fixed Remove drupal_classloader() use in Drupal\Core\AnnotatedClassDiscovery.

Issue #1763640 by beejeebus, alexpott, Jose Reyero, c31ck, das-peter, YesCT, heyrocker, Gábor Hojtsy: Introduce config context to make original config and different overrides accessible.

Issue #1914366 by vijaycs85, Gábor Hojtsy, alexpott: Move all configuration schema files into a schema subdirectory.

Issue #1910318 by katbailey: Make path resolution the responsibility of a series of PathProcessor classes, rather than one PathSubscriber class.

Issue #1515312 by heyrocker, beejeebus, alexpott, xjm, realityloop, sun: Added snapshots of last loaded config for tracking whether config has changed.

Issue #1798214 by tnightingale, g.oechsler, fubhy, katbailey, effulgentsia, Crell, dipen chaudhary: Upcast request arguments/attributes to full objects.