Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #1875996 by Xano, tim.plunkett, neclimdul, Rajendar Reddy, Jalandhar: Reconsider naming conventions for derivative classes.

Issue #2078879 by pwolanin, dawehner, Xano: Fixed DerivativeDiscoveryDecorator doesn't check/enforce the proposed derivative fetchers implement interface DerivativeInterface.

Issue #2028511 by damiankloip, dawehner: Allow plugin derivative classes to use services from the container.