Optimize the log updating

[JuhaS]

Currently when you run a pipeline the UI will poll the logs endpoint until it finishes. This means every time it will fetch all of the logs which is far from optimal.

Solutions:

• 1. Send row-start number to the logs endpoint to tell backend to only return rows after row-start. UI would then merge the given rows to the previous rows.
• 2. Implement websocket to stream the logs to frontend.

For long term the websocket sounds better, and we can leverage it for other things as well.