[fronius] Add Autonomy and Self Consumption channels (#12420)

[fronius] Add Autonomy and Self Consumption channels (#12420)

* Add Autonomy and Self Consumption channels
* Change Inverter channels from DecimalType to QuantityType
* Convert ValueUnit to QuantityType, honour the unit from ValueUnit
* Replace custom unit converter with QuantityType's unit conversion
* Return QuantityType of zero for missing ValueUnit data, to be consistent with P_AC.
* Return UnDefType.NULL for other missing data
* De-duplicate URL parsing routine

Signed-off-by: Jimmy Tanagra <jcode@tanagra.id.au>