Issue #3261486 by catch, longwave, dww: Remove core updates added prior to 9.3.0 and adjust test coverage

Issue #3254726 by longwave, mondrake: Remove SimpleTest support from run-tests.sh, TestDiscovery and TestRunnerKernel

Issue #3254727 by Leon Kessler, ranjith_kumar_k_u, cmlara, andileco: File links with query parameters no longer work

Issue #3164210 by jungle, sylus, Akhildev.cs, dww: Refactor array_merge() usage in loops as possible for performance

Issue #2807949 by kunal.sachdev, tim.plunkett, tedbow, Dropa: update.module is incorrectly only responding when modules are installed

Issue #3097889 by longwave, paulocs, anushrikumari, SenthilMohith, andypost, Gábor Hojtsy, catch, lauriii, Wim Leers: Remove deprecated theme functions

Revert "Issue #3262500 by catch, andypost: Mark drupal_find_theme_functions() @internal in Drupal 9"

This reverts commit f64e3344.

Issue #3065574 by Charlie ChX Negyesi, quietone, amateescu: getUntranslated() doesn't refer to anything

Issue #3172166 by Pooja Ganjage, ekes, Megha_kundar, xjm, alexpott, tstoeckler, mbovan, Spokje: Element::properties() produces notices if given an array with integer keys

Issue #3261957 by longwave, quietone, andypost: Properly deprecate migrate_drupal_multilingual for future removal

Issue #3258030 by hooroomoo, lauriii, andregp, Wim Leers, rkoller: Text fields using CKEditor 5 do not get visual error indicator

Issue #3248469 by nod_, lauriii, Wim Leers, longwave: Research if the CKE off-canvas CSS reset could be optimized

Issue #3261264 by andypost: Remove deprecated code from \Drupal\Core\Cache\DatabaseCacheTagsChecksum

Issue #3249592 by hooroomoo, vlyalko, Wim Leers, lauriii: [drupalImage] <img width> upcast assumes HTML5: px unit, but HTML4 allowed % unit

Issue #3258435 by ravi.shankar, alexpott, longwave: Remove deprecated feed.reader.* and feed.writer.* services from the container

Issue #3261743 by Spokje: Remove @composer require phpspec/prophecy-phpunit:^2 from "drupal-phpunit-upgrade"

Issue #3261712 by Wim Leers, bnjmnm: Expand SmartDefaultSettingsTest to also test a format + editor with media embedding