download view controller: remove singleton

References #198
3 jobs for !252 with splitdownloads in 17 minutes and 11 seconds (queued for 2 seconds)
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Status Job ID Name Coverage
  Lint
passed #453848
macos
lint

00:04:03

 
  Build
passed #453849
macos
iOS 12.0

00:06:40

passed #453850
macos
tvOS 12.0

00:06:27