[Refactor] split runtime initialization (create, connect, init) in cli scripts

[enyst]

Give a summary of what the PR does, explaining any non-trivial design decisions.

This PR proposes to:

• fix a regression in Add selected_repo to command line #6949 where not all occurrences were handled, resulting in a double call to runtime.connect in a couple of entry points (eval_infer.py, one method in the resolver)
• do runtime initialization in three basic steps (create, connect, initialize)

I was just looking to clean up the runtime from agent, when I saw that not all occurrences were handled previously. 😓 We also have documentation that specifies connect so this PR proposes to restore that part (the separate create and connect), and add an initialize for the specific cases of selected_repo in cli and headless.

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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:19499fc-nikolaik   --name openhands-app-19499fc   docker.all-hands.dev/all-hands-ai/openhands:19499fc