Update extension fields of BidRequest and its sub structs. Change them to json.RawMessage.
Here are two reason to do that:
1: Avoid the loss of precise while unmarshal data to interface{}. The build-in json and easyjson both use the type of float64 to parse a number in json string. If it is an int64 number, some information will loss.
2: Avoid the change between interface{} and specified structs. Using json.RawMessage can make sure there is only one convert from the beginning.
This is the second part of this work, update device's extension.