Create an operating mode element for HPWHs

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E.g.:

• "standard" (sometimes called auto or hybrid)
• "heat pump only" (sometimes called efficiency or economy)
• "electric only" (sometimes called heater)
• "other"

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Manufacturers use different terminology. Here is EPA's terminology: https://www.energystar.gov/products/water_heaters/high_efficiency_electric_storage_water_heaters/how_it_works

Here are Rheem's modes: https://lildutchuncle.com/rheem-hybrid-water-heater-modes-explained/