Rename Catena4802::ReadVin (or remove it)

[terrillmoore]

A spurious API was added for the Catena4802, "read vin". This is reading vbat. We never know whether a battery voltage is a actually a battery, renaming was a bad idea because it breaks compatibilty. Futhermore, ReadVin implies that it's an arbitrary analog voltage. It's a bad name if we're actually reading a supply voltage. Since it's reading Catena480x::ANALOG_CHANNEL_VBAT, it is clear that either the name of the channel is wrong or the name of the API.

Solution:

• Deprecate ReadVin immediately
• Replace with "ReadVbat" (and implement by calling) the ReadVbat used by other other Catenas;
• Remove ReadVin remove in next major version.