Revert "Issue #2165725 by Xano: Introduce hook_entity_operation()."

This reverts commit 2cf87103b55d6f9ece06be4e83c481425182a60d.
Issue #2226183 by alexpott: Running PHPUnit tests through run-tests.sh is unnecessarily slow.
Issue #2199381 by slashrsm, Xano: Add \Drupal\Core\Path\PathInterface.
Issue #2207893 by dawehner, pwolanin, jessebeach, Boobaa: Convert menu tree building to a service.
Issue #2108813 by cilefen, mtift, Désiré, xjm, InternetDevels: Add fancier config import/export test scenario.
Issue #2225677 by Eli-T, mcjim: Fix naming in ResponsiveImageMappingEntityTest following module rename from Picture to Responsive Image.
Issue #2115391 by jhodgdon, lokapujya, zaporylie, BrightBold: Numbers are displayed in search results list.
Issue #2225685 by ocsilalala: BanIpManager doesn't have interface.
Issue #2201693 followup by plopesc, Sweetchuck, rodrigoaguilera: Field output supporting code should move out of field.module.
Issue #2111887 by Gábor Hojtsy, kfritsche, vasi1186, dclavain, YesCT, segi: Regression: Only title (of base fields) on nodes is marked as translatable.
Issue #2225333 by Boobaa: LogicException in Drupal\hal\Normalizer\FieldItemNormalizer does not exist.
Issue #2111887 follow-up by ianthomas_uk: Fix broken HEAD.
Issue #2224691 by Sweetchuck: JavaScript Drupal.t and Drupal.formatPlural only works for non-english languages.
Issue #2218027 by eojthebrave, jhodgdon: Improve the D8 api.d.o landing page.
Issue #2210177 by andypost: [Followup] Use getSetting() in comment formatter.
Issue #2090525 by batigolix, ellishettinga, visabhishek, lostkangaroo, rak2008: Update hook_help for menu module.
Issue #2219617 by visabhishek, galooph, joshtaylor, Cottser: Remove @ingroup themeable from preprocess function docblocks.
Issue #2226185 by galooph, filijonka, Cottser: Remove @ingroup themeable from core theme Twig template docblocks.
Issue #2225649 by jjcarrion, LewisNyman: Action links on /admin/config/services/aggregator are inside of an <em> tag.
Issue #2056879 by martin107, Outi, ioskevich, Cottser: Improve twig_* vars DOCs in settings.php and make Twig debug markup require a cache clear.