Revert "Issue #2459753 by tim.plunkett: EntityForm::validate() should be able to modify the form structure"

This reverts commit d4d83576.

Issue #1919930 by tim.plunkett, nlisgo: Bundle entity form IDs violate module namespaces (both on server-side + front-end CSS)

Issue #2421263 by alexpott, formatC'vt, kim.pepper, andypost, larowlan, chx: Potential data loss: concurrent (i.e. by different users) node edits leak through preview

Issue #2421581 by amateescu: Node preview causes stale values to be kept indefinitely for exisiting nodes

Issue #2406103 by Berdir, alexpott: Remove hook_node_validate() and hook_node_submit() because they bypass the entity API

Issue #2230637 by plach, fran seva, yched, swentel: Create a Language field widget and the related formatter

Issue #2355909 by penyaskito, alexpott, Gábor Hojtsy, DuaelFr: language.settings config is not scalable

git commit -m 'Issue #2377397 by Wim Leers, alexpott: Themes should use libraries, not individual stylesheets'

Issue #2340667 by YesCT, Pedro Lozano, alexpott, martin107: Protect Drupal\Core\Language\Language::id, and use getId().

Issue #2277103 by tim.plunkett, pwolanin, Wim Leers, dawehner, hotpizzas: Switch Drupal::l() and LinkGenerator to expect a Url object.

Issue #2343651 by xjm, tim.plunkett, Wim Leers, dinarcon, dawehner: Remove most remaining l() calls.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.

Issue #2022875 by Berdir, alexpott, Xano, swentel, tim.plunkett, vladan.me: Resolve difference between submitForm(), submit(), and save() in EntityFormController.

Issue #2324121 by Berdir, slashrsm, alexpott: Fixed NodeType's settings array was meant to be able to store information from mutliple modules.

Issue #2226493 by Berdir, Wim Leers, m1r1k, mr.baileys, andypost, scor, cbr, joelpittet: Apply formatters and widgets to Node base fields.

Issue #2313931 by Berdir: Merge ['controller'] with ['build_info']['callback_object'] and add a method for it.

Issue #2309323 by Berdir, tim.plunkett: Allow #submit and #validate to be specified as methods of the form object.

Issue #1510544 by swentel, Bojhan, Gábor Hojtsy, merlinofchaos, Cottser, Wim Leers, plopesc, aspilicious, sannejanssen,  larowlan, tim.plunkett, nod_: Fixed Show previews in front-end theme, able to select different view modes.

Issue #2308821 by tim.plunkett: Replace FormErrorInterface with $form_state->setErrorByName() and $form_state->setError().

Issue #2272481 by herom, ParisLiakos, tim.plunkett: Remove usages of watchdog() from forms, plugins and controllers.

Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom, rhm50, naveenvalecha, andypost,  mandar.harkare, sergeypavlenko, sidharthap, SIz, tkuldeep17: Replace user_access() calls with ->hasPermission() in all core modules except user.

Revert "Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom: Replace user_access() calls with ->hasPermission() in all core modules except user."

Fixing commit credit.

This reverts commit 25afa810.

Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom: Replace user_access() calls with ->hasPermission() in all core modules except user.

Issue #2124957 by Wim Leers, catch: Replace 'content' cache tag with 'rendered' and use it sparingly.

Issue #2246665 by jaredsmith, martin107, YesCT, filijonka, tstoeckler: Typehint with Drupal\Core\Language\LanguageInterface instead Drupal\Core\Language\Language.

Issue #2248991 by marco, tstoeckler, xjm: Rename the 'log' field to 'revision_log' in Node and CustomBlock.

Issue #2064639 by rahul.shinde, InternetDevels, martin107, longwave, jayeshanandani, connork, CarlHinton, vlad.n, superspring, andrei.dincu, stevepurkiss, jlindsey15, Salah Messaoud: Fixed Remove unused local variables from the node module.

Issue #2183231 by tstoeckler, plach, jessebeach, fago, Berdir, xjm, mauzeh: Make ContentEntityDatabaseStorage generate static database schemas for content entities.

Issue #216064 by Xano, idflood, drifter, Artusamak, ygerasimov, sun, ParisLiakos, Cottser, TravisCarden, marcingy, floretan, catch, tedbow: Entity form "Delete" button triggers server-side + HTML5 form validation; change "Delete" button to a link.