Issue #2271363 by Berdir: Remove CacheDecorator and ProcessDecorator.

...ib/Drupal/Component/Plugin/Discovery/ProcessDecorator.php

core/lib/Drupal/Component/Plugin/PluginManagerBase.php

core/lib/Drupal/Core/Menu/LocalActionManager.php

core/lib/Drupal/Core/Plugin/Discovery/AlterDecorator.php

core/lib/Drupal/Core/Plugin/Discovery/CacheDecorator.php

core/lib/Drupal/Core/Validation/ConstraintManager.php

core/modules/system/src/Tests/Plugin/AlterDecoratorTest.php

...es/system/src/Tests/Plugin/CacheDecoratorLanguageTest.php

core/modules/system/src/Tests/Plugin/CacheDecoratorTest.php

.../system/tests/modules/plugin_test/plugin_test.routing.yml

...m/tests/modules/plugin_test/src/Controller/PluginTest.php

...lugin_test/src/Plugin/AlterDecoratorTestPluginManager.php

...modules/plugin_test/src/Plugin/CachedMockBlockManager.php