Addressing stage 1 of ATLASRECTS-7683, this introduces structs of parameters which are habitually used together (such as all the fit parameters for the pixel ToT/charge calibration) and uses these types for setters and getters in the PixelChargeCondData interface. In this initial stage, it makes the interface busier; eventually these will replace the legacy methods and the interface will be cleaner (as well as cleaning up PixelChargeCalibAlgs). unit tests of these new interfaces are also given.