Issue #3405800 by alexpott, phenaproxima, Wim Leers, bircher, larowlan: Config collections do not trigger configuration events consistently

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

Issue #2524082 by pfrenssen, Gábor Hojtsy, Wim Leers, Berdir, Fabianx, dawehner, catch: Config overrides should provide cacheability metadata

This reverts commit 434fd08b.

This reverts commit b5b92b5c.

Issue #2224887 by alexpott, Berdir, Gábor Hojtsy, Jalandhar: Language configuration overrides should have their own storage.

Issue #2219499 by Berdir, alexpott, Gábor Hojtsy, vijaycs85, swentel: Generalize language config override responsibility.

Issue #2215503 by Gábor Hojtsy, Wim Leers: Use services instead of event subscribers for config module overrides.