Fix fd leak

[tofarr]

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This is ongoing work in file descriptor leaks, related to multiple PRs:

• Revert "Fix file descriptor leak (#6897)" #6921
• Fix file descriptor leak #6897
• Fix: File Descriptor leak #6883

The previous issue was that there was some LiteLLM implementations which created multiple httpx clients and never closed any of them (Claude), some which closed their connections (Proxy), and some which used a semi global shared httpx client which is never closed (OpenAI).

In the last incarnation, the OpenAI model caused issues, which should now be resolved using the proxy client. The proxy client will close connections when asked, but transparently reopen them if requested (Similar to the requests library)

Once our LiteLLM PR is merged, we will be able to revisit (and hopefully remove) this.

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:09e46e9-nikolaik   --name openhands-app-09e46e9   docker.all-hands.dev/all-hands-ai/openhands:09e46e9