completely rebuilt the smart_network_asset_loader.dart with added new features

[A-dalyomer]

priority handling, server file creation date and complete code refactoring

[bw-flagship]

@A-dalyomer I see what you're doing here and it makes sense. However, it's a very opinionated implementation and includes a new dependency. Therefore, I would not merge this. Instead, you can keep it as a fork for your project.