instruments/energy_measurments: Improve instrument description
instruments/energy_measurments: Improve instrument description

Add note to users that all configuration for the backends should be
added through this instrument rather than directly.

lisatn/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,lisatn/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,lisatn/workload-automation,lisatn/workload-automation,setrofim/workload-automation,setrofim/workload-automation,ARM-software/workload-automation