Thanks to @nobert
HA 2022.7 supports native temperature conversions with per-entity preferences for units of measurement. However, this change had the side effect of causing all temperatures emitted by the SensorPush integration to be in Fahrenheit.
This PR updates the integration to use the new "native" temperature values, and refactors it a bit to remove the old internal metric/imperial logic. It now always uses imperial measurements (though no longer relies on the old unit of measurement config setting), and lets HA do any conversions with the new mechanism.