Issue #3109556 by finnsky, nod_, longwave, effulgentsia, Ambient.Impact: Update from Yarn 1 to Yarn 4

Issue #3355381 by catch, drewcking, stewest, lauriii, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS

Revert "Issue #3355381 by catch, drewcking, stewest, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS"

This reverts commit 56e2560a.

Issue #3355381 by catch, drewcking, stewest, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS

Issue #3373328 by catch, keshav.k, Ambient.Impact, longwave: ^10.1 CSS aggregation breaks during maintenance mode

Issue #2998451 by bnjmnm, HOG, lauriii, ndf, gaurav-mathur, Ambient.Impact, Chi, nod_, andy-blum, droplet: Toolbar tray rendering can result "flickering" resizing of content area to accommodate open trays

Issue #3027639 by catch, jonhattan, ankithashetty, Lal_, voleger, beunerd, cmlara, yogeshmpawar, Jose Reyero, drfuzetto, MiguelArber, smustgrave, longwave, Berdir, leandro713, Ambient.Impact, olli, amitaibu: Make css/js optimized assets path configurable

Issue #3088168 by DuaelFr, dww, Ambient.Impact, alexpott: Media thumbnail dimensions are wrong for YouTube videos

Issue #3192234 by heddn, pivica, Qusai Taha, yogeshmpawar, bingolitte, Phil Wolstenholme, smustgrave, Berdir, devkinetic, maximpodorov, ranjith_kumar_k_u, nikitagupta, ankithashetty, vsujeetkumar, pooja saraah, timohuisman, glynster, Luke.Leber, Ahmad Abbad, flyke, chetanbharambe, Graber, zcht, sasanikolic, John Pitcairn, catch, Rar9, Anybody, Ambient.Impact, alexpott, manarak, Fabianx, longwave, benmorss, Martijn de Wit, Wim Leers, larowlan: Apply width and height attributes to allow responsive image tag use loading="lazy"

Issue #3191468 by Gábor Hojtsy, xjm, ckrina, DeepaliJ, bskibinski, Deepthi kumari, catch, Neslee Canil Pinto, Dennis Cohn, boulaffasae, bnjmnm, andypost, aleevas, antonellasevero, anu.a_95, bandanasharma, atul4drupal, cedric_a, codersukanta, Hardik_Patel_12, Krzysztof Domański, hash6, himanshu_sindhwani, heykarthikwithu, HOG, fhaeberle, Dinesh18, design.er, DyanneNova, effulgentsia, ethomas08, emma.maria, Adam Szalapski, kostyashupenko, tedbow, vishalchandna, volkerk, aburrows, Pls, martin107, lauriii, alwaysworking, VD39, anand.toshniwal93, dawehner, justafish, iKb, eojthebrave, finnsky, Ambient.Impact, tunic, alexpott, andrewmacpherson, antoineh, anmolgoyal74, slip, rsau, lhuria94, jeevanbhushetty, porkloin, progga, rahul01, pwilson, hudri, huzooka, ravi.shankar, reinchek, rensingh99, sauravk, saschaeggi, ranjith_kumar_k_u, SharmaAnmol, pradeepjha, prabha1997, pranav45, priyanka.sahni, rainbreaw, quiron, sd9121, shaal, tim.plunkett, thekishanraval, yoroy, nod_, Devipriya Rajamanickam, Archita Arora, thalles, tanubansal, Vinodhini.E, shashikant_chauhan, shimpy, sibustephen, swatichouhan012, siddhant.bhosale, pminf, phenaproxima, kiran.kadam911, katrienc, KondratievaS, Kristen Pol, Lal_, L2G2, katherined, katannshaw, Indrajith KB, imganesh, Jongruk Timmanee, iro, kapilkumar0324, joseph.olstad, Lendude, Maithri Shetty, mrinalini9, mradcliffe, narendra.rajwar27, neelam_wadhwani, olli, Peter Majmesku, modulist, mfairchild365, komalk, kishor_kolekar, martijn.cuppens, Meenakshi.g, Vidushi Mehta, Neetika K: Retire "Admin UI and JavaScript Modernisation" initiative in favour of "Decoupled menus" and the upcoming "Easy out of the box" initiative

Issue #3057772 by katherined, sd9121, boulaffasae, bnjmnm, komalkolekar, lauriii, KondratievaS, ckrina, DyanneNova, Ambient.Impact, sirtet, andrewmacpherson, yoroy: Ambiguous icons for collapsing/expanding menu items