Issue #3432482 by mondrake, smustgrave: Remove deprecated code from the Cache API

core/lib/Drupal/Core/Cache/ApcuBackend.php

core/lib/Drupal/Core/Cache/ApcuBackendFactory.php

core/lib/Drupal/Core/Cache/Cache.php

core/lib/Drupal/Core/Cache/CacheTagsChecksumTrait.php

...rupal/Core/Cache/Context/MenuActiveTrailsCacheContext.php

core/lib/Drupal/Core/Cache/DatabaseBackend.php

core/lib/Drupal/Core/Cache/DatabaseBackendFactory.php

core/lib/Drupal/Core/Cache/MemoryBackend.php

core/lib/Drupal/Core/Cache/MemoryBackendFactory.php

.../lib/Drupal/Core/Cache/MemoryCache/MemoryCacheFactory.php

core/lib/Drupal/Core/Cache/MemoryCounterBackendFactory.php

core/lib/Drupal/Core/Cache/PhpBackend.php

core/lib/Drupal/Core/Cache/PhpBackendFactory.php

...ib/Drupal/Core/CacheDecorator/CacheDecoratorInterface.php

core/tests/Drupal/Tests/Core/Cache/CacheTest.php