[C++][cpprest] Add Petstore test for C++ (cpprest) API client

[wing328]

Description

Similar to Qt5 C++, we want to add Petstore test for C++ (cpprest) API client so that we run integration tests as part of the CI.

Swagger-codegen version

Latest master

Suggest a Fix

A good starting point is to look at the tests for Qt5 C++: https://github.com/swagger-api/swagger-codegen/tree/master/samples/client/petstore/qt5cpp/PetStore