external code execution
ExternalEvaluate["sys", "cmd"]
ExternalEvaluate[{"sys", opts}, "cmd"]
ExternalEvaluate[assoc, "cmd"]
ExternalEvaluate[obj, "cmd"]
ExternalEvaluate[session, "cmd"]
ExternalEvaluate[sys -> "type", …]
ExternalEvaluate[spec, obj]
ExternalEvaluate[spec, assoc]
ExternalEvaluate[spec, {cmd1, cmd2, …}]
ExternalEvaluate[DatabaseReference[ref], "cmd"]
ExternalEvaluate[spec]