Propagate connector persister errors

Right now connector persister errors are only logged but not propagated back to the Conduit runtime. We need to make sure that an error in the connector persister is sent back to the Conduit runtime which then initiates a shutdown.

Start by tracing how connector persister errors are currently logged and how the Conduit runtime handles shutdown signals. Identify the existing error path and related tests, then verify that a persister error reaches the runtime and initiates shutdown.

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