v0.53.0

- Node: Split ChatService into AuthenticatedChatService and
  UnauthenticatedChatService. We plan to make a similar split for the
  other platforms in the future.

- Node: Upload Breakpad syms files for debug info instead of using
  per-platform formats

- Server: Added SealedSenderMultiRecipientMessage#serializedRecipientView,
  to save on repeated parsing

- iOS: ComparableBackup is now correctly implemented as
  simulator-only, fixing builds for device broken in v0.52.4