Deserialize fixture values

[skarimo]

Previously we serialized the responses again so that we can compare bdd fixtures with the actual response objects. For example take a look at the failure below:

   ✖ And the response "widgets[0].definition.requests[0].style" is equal to {"palette": "warm","line_type": "solid","line_width": "normal"} # features/step_definitions/request_steps.ts:255
       AssertionError
           + expected - actual

            {
           -  "lineType": "solid"
           -  "lineWidth": "normal"
           +  "line_type": "solid"
           +  "line_width": "normal"
              "palette": "warm"
            }

To avoid the above, we used to serialized the response so that keys get remapped properly lineType -> line_type.

This PR deserializes the fixtures values instead of the serializing response again for comparing.