core (launcher): new `wait_for_service` option: if `wait_for_service` is used in `[DEFAULT]`, the service at the specified host/port is waited for before starting the backend. This is useful in the situation where we need to be sure that something is started before running, e.g. in a container.

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−these certificates are used for demo purpose only. Those must be the same as in
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−backend_e2e (they are generated there)