Add class `measurement` to power sensor (#4400)

This allowed me to add the sensor to the energy dashboard to make the "now" tab show the current use power for the heat pump

custom_components/tuya_local/devices/henden_essential_pool_heatpump.yaml

@@ -138,6 +138,7 @@ entities:
         type: integer
         unit: W
         optional: true
+        class: measurement
         # DPS 113 value is False, but
         # power _is_ correctly reported on DPS 112
         # - id: 113