Issue #2476407 by borisson_, hussainweb, znerol, Fabianx, Wim Leers, dawehner, Crell, Berdir: Use CacheableResponseInterface to determine which responses should be cached

Issue #2018411 by ParisLiakos, tim.plunkett, msonnabaum: Figure out a nice DX when working with injected translation.

Issue #1987712 by dawehner, claudiu.cristea, damiankloip, andypost: Convert file_download() to a new style controller.