When the user is prompted for a deployment name during `langgraph deploy`,
the value is now persisted to the local .env file so subsequent runs
skip the prompt and reuse the saved name.
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>