Go generation for optional parameters

[baywet]

pending on #413

Go does not have support for optional parameters, nor does it support methods/functions overloads. We're leveraging such language functionalities in other languages so people without the need to provide query parameters/middleware options/request headers/a native response handler for as single request do not need to write .get(nil, nil, nil, nil) and can just write .get() instead.

Options to consider

• generate overloads with different names (might be ugly)
• align with azure go sdk guidelines and generate additional request options classes with one parameter for each original parameter, so people can just call .get(nil) (suggestion from @jhendrixMSFT on an internal thread)
• investigate other options?

@darrelmiller to lean on the architecture/usage side.

[baywet]

the decision was made to use options classes.