Function probe_cloud 

fn probe_cloud() -> CloudInfo

Run all vendor probes in parallel (one OS thread per vendor).

Join order follows the PROBES precedence list: the first successful probe wins and the remaining [JoinHandle]s are dropped without joining, so those threads keep running until their own timeouts (avoids waiting for every vendor on, e.g., a confirmed AWS host). Each HTTP call uses IMDS_TIMEOUT.