Mutually-exclusive requirements in schema should translate into cpp object population code

[tanaya-mankad]

Currently, a requirement such as

regular_interval:
      Description: Duration of regular interval
      Data Type: Numeric
      Units: s
      Constraints: ">0"
      Required: "if !timestamps"
timestamps:
      Description: Array of timestamps
      Data Type: "[Timestamp][1..]"
      Required: "if !regular_interval"

translates as:

json_get<double>(j, "regular_interval", x.regular_interval, x.regular_interval_is_set, true);
json_get<std::vector<std::string>>(j, "timestamps", x.timestamps, x.timestamps_is_set, true);

which doesn't take into account the mutual exclusivity.