Removed connections, logger, neofs because they were moved to sdk repo.
Made changes in downloader, uploader, main.go and app.go via
refactoring of neofs.
Replaced dependencies to removed packages by sdk packages.
Signed-off-by: Angira Kekteeva <kira@nspcc.ru>
Use standard error wrapping/unwrapping instead. The conversion is mostly
straightforward, but see grpc/grpc-go#2934 for GRPC `status.FromError`, it
doesn't currently support unwrapping/errors.As(), so we're unwrapping manually
here.
