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 #3397490 by quietone, smustgrave, xjm, longwave, poker10: Fix more words that are only misspelled in comments

Issue #3209617 by longwave, daffie, catch: [Symfony 6] Symfony\Component\HttpFoundation\RequestStack::getMasterRequest() is deprecated, use getMainRequest() instead

Issue #2238561 by alexpott, dawehner, andypost, bradjones1, ridhimaabrol24, jofitz, eiriksm, Darren Oh, kalyansamanta, znerol, neclimdul, catch, pwolanin: Use the default PHP session ID instead of generating a custom one

Issue #3104307 by Berdir, longwave, Gábor Hojtsy, Wim Leers, alexpott, andypost: Remove  BC layers in various Drupal\Core components

Issue #3025867 by tim.plunkett, Kristen Pol, phenaproxima, alexpott, xjm, andypost: Provide a classed object for TempStore metadata

Issue #2860341 by heddn, juampynr, seanB, RumyanaRuseva, ephod, stephsem23: PrivateTempStore->getOwner Attempts to access possibly unset Request Session

Issue #2743931 by aaronbauman, gambry, harsha012, joachim, acbramley, rackberg, koryp, DedMoroz, akalam, Yogesh Pawar, alexpott, alexej_d, larowlan, stefan.r, unstatu, sathish.redcrackle: Saving to the private tempstore doesn't start a session for anonymous users