Issue #1862750 by fubhy, Berdir, dawehner: Implement entity access API for nodes.

core/lib/Drupal/Core/Entity/EntityAccessController.php

...ib/Drupal/Core/Entity/EntityAccessControllerInterface.php

...k/lib/Drupal/custom_block/CustomBlockAccessController.php

core/modules/node/lib/Drupal/node/NodeAccessController.php

.../modules/node/lib/Drupal/node/Plugin/Core/Entity/Node.php

...les/node/lib/Drupal/node/Tests/NodeAccessLanguageTest.php

core/modules/node/node.module

...est/lib/Drupal/entity_test/EntityTestAccessController.php

core/modules/user/lib/Drupal/user/UserAccessController.php