Function shape_to_string

tests/test_metal_python_ref_compare.cpp:32–39

};

static std::string shape_to_string(const std::vector<int> & shape) {
    std::string s;
    for (size_t i = 0; i < shape.size(); ++i) {
        if (i > 0) s += "x";
        s += std::to_string(shape[i]);
    }
    return s;
}

static metric_row compute_metrics(const std::string & tensor,
                                  const float * got,