Fix MeasureEnergyArray impl array size

getEnergyConsumptionData wrongly set the MeasuredEnergyArray size to the
received EnergyConsumerResult array. Instead the size should be equal to
the number of valid Subsystems added to the array.
Also add BatteryExternalStatsWorkerTest to FrameworkServicesTests

Fixes: 178747292
Test: atest FrameworksServicesTests:BatteryExternalStatsWorkerTest
Change-Id: I43793c7ddf9ff1b1badf478c0d9c3accb1a328d5