Since we now generate file classes even for IR loaded from dependencies
(see 3a9b94235f) to simplify code in certain lowerings, it makes sense
to do that for all source files together before any meaningful
lowerings. The easiest way to do so is to make FileClassLowering a
module-wide phase.
ExpectDeclarationsRemoveLowering is now also a module-wide phase because
it needs to be run before FileClassLowering (to avoid producing empty
facades for files that only contain `expect` declarations)
Alexander Udalov
5341de253f