Issue #2030571 by calebtr, daffie, filijonka, YesCT, Thomas Brekelmans, alexpott, Mile23, tadityar, Sharique, tim.plunkett, boztek: Expand Block with methods

Issue #2339151 by EclipseGc, tim.plunkett, Gábor Hojtsy, effulgentsia: Conditions / context system does not allow for multiple configurable contexts, eg. language types

Issue #2278541 by tim.plunkett, kim.pepper, Bojhan, EclipseGc: Refactor block visibility to use condition plugins.

Issue #1847002 by tim.plunkett, effulgentsia, msonnabaum: Move entity type classes from Drupal$provider\Plugin\Core\Entity to Drupal$provider\Entity.

Issue #1391694 by tim.plunkett, aspilicious, fago, pounard, plach, Crell, msonnabaum, tstoeckler: Use type-hinting for entity-parameters.

Issue #1871696 by tim.plunkett, xjm, sun, msonnabaum, EclipseGc: Convert block instances to configuration entities to resolve architectural issues.

Issue #1535868 by EclipseGc, tim.plunkett, xjm, Jody Lynn, sdboyer, naxoc, tizzo, effulgentsia, dawehner, disasm, beejeebus: Convert all blocks into plugins.