Add support for Vitocal 300-G (CU401B) features

[lackas]

Request to add support for Vitocal 300-G (CU401B) heat pump features:

HeatPump class:

• COP methods: getCoefficientOfPerformanceHeating/DHW/Total/Cooling/Green
• Compressor: getPower, getPowerUnit, getModulation, getModulationUnit
• Pressure sensors: getHotGasPressure, getSuctionGasPressure (with units)
• Temperature sensors: getHotGasTemperature, getLiquidGasTemperature, getSuctionGasTemperature
• Runtime: getMainECURuntime, getHeatingRodRuntimeLevelOne/Two
• Configuration: buffer temp max, damping factor, heater approvals
• New CoolingCircuit class with getType, getReverseActive

HeatingDevice class:

• Primary circuit pump: getPrimaryCircuitPumpRotation (with unit)
• Circuit temperature: getTemperature
• Fallback paths for hotWaterStorage vs dhwCylinder naming variants

Compressor class:

• Load class methods now support fallback to statistics.load path

Implemented in PR #688.

[lackas]

All features from this issue have been implemented and merged into master via #689 (COP, compressor sensors, refrigerant circuit, heating rod stats) and #706 (CoolingCircuit support). Closing.