Adding the support tracing of child models invoked from a BLS model

[oandreeva-nv]

To allow tracing for sub models, user must provide request when creating InferenceRequest object in python model.
Sample:

for request in requests:
           ...

            infer_request = pb_utils.InferenceRequest(
                model_name=model_name_string,
                requested_output_names=["OUTPUT0", "OUTPUT1"],
                inputs=[in_0, in_1],
                request=request)

This is necessary, because request has an access to the main trace. Open to the discussion on this.