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

Issue #2432791 by alexpott, vijaycs85, tim.plunkett, joshtaylor, Fabianx, Berdir, yched, bojanz: Skip Config::save schema validation of config data for trusted data.

Issue #2204697 by alexpott, tstoeckler, mauzeh, Berdir: Move getConfigPrefix() to ConfigEntityTypeInterface