Allow users to deploy to langsmith deployments from the langgraph-cli.
This PR makes the following changes:
1. Add a simple host backend client with httpx
2. Adjust `progress.py` to show elapsed time for commands, and also use
threading.Event to stop the spinner
3. Adjust `_build` to allow arbitrary command so we can pass `docker
buildx build` and default to `docker build`
4. Add new `deploy` command, this re-uses a lot of the `langgraph build`
functionality, and then uses the new host-backend client to push the
built image to langsmith deployments.
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Co-authored-by: David Asamu <david.asamu@langchain.dev>
