Allow ServiceDelegate to parse type unions from factory methods

[cspray]

1.3 releases a feature that allows the #[ServiceDelegate] attribute to determine what type it is responsible for by parsing the return type of the method. Currently this does not support type unions but could. Need to figure out a way to do this that limits the amount of backward compatibility breaks and done so in a way that will work with a variety of containers that may not be TypeUnion aware.