Issue #3431452 by godotislate, smustgrave, alexpott: Rename RenderElement and FormElement plugin abstract classes to RenderElementBase and FormElementBase

Issue #3421439 by godotislate, sorlov, quietone, smustgrave, alexpott, larowlan, longwave, andypost: Convert form and render element plugin discovery to attributes

Issue #3351004 by Natallia: Deprecations for PHP 8.1 get_class() and get_called_class() without argument

Issue #77245 by drpal, tedbow, nod_, phenaproxima, Wim Leers, googletorp, rteijeiro, vineet.osscube, tim.plunkett, idflood, joelpittet, pk188, lauriii, BarisW, lokapujya, chr.fritsch, droplet, andrewmacpherson, dmsmidt, dawehner, alexpott, jessebeach, NickWilde, DuaelFr, Cottser, seutje, samuel.mortenson: Provide a common API for displaying JavaScript messages

Issue #3002522 by andypost, Matthijs, tim.plunkett, wizonesolutions: Calling StatusMessages::renderMessages() with a  returns a faulty render array

Issue #2935255 by Jo Fitzgerald, kim.pepper, voleger, alexpott, martin107, jibran, catch: Remove all usages of drupal_get_message and drupal_set_message in core lib

Issue #2853509 by alexpott, xjm, nod_, dmsmidt, dawehner, catch, graber: Don't render status messages if there are no messages but also include their assets if there might be

This reverts commit 78ca5677.

Issue #2773333 by Berdir, Juterpillar, Wim Leers, Fabianx, renukakulkarni: Form validation errors, status messages on form submission are shown after page refresh when form is rendered in block

Issue #2751121 by tstoeckler, kiamlaluno: class StatusMessages documentation page contains incorrect markup

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2478483 by Wim Leers, Fabianx: Introduce placeholders (#lazy_builder) to replace #post_render_cache

Issue #2289917 by Wim Leers, mdrummond, lauriii, Manuel Garcia, emma.maria, Scionar, davidhernandez: Convert "messages" page element into blocks