[Roadmap] Optimize agent stepping efficiency

[dandansamax]

Current agents take at least 20 seconds per step, which is even worse when facing multi-environment. We target to shorten the step time to lower than 10 seconds for two envirnments setting.

• [ ] Compress screenshot images to improve network tranfering speed. (Currently we use uncompressed PNG format encoded by base64)
• [ ] Package all deep learning models as micro-services so that they can be deployed to a remote server with high performance GPUs.