Function backend_is_available

tests/unittests/test_conv_transpose_fast_path.cpp:110–117

        const ggml_status status = ggml_backend_graph_compute(backend, graph);
        const auto end = std::chrono::steady_clock::now();
        if (status != GGML_STATUS_SUCCESS) {
            std::ostringstream oss;
            oss << "backend graph compute failed with status " << static_cast<int>(status);
            throw std::runtime_error(oss.str());
        }
        RunResult result{output.shape, {}};
        result.compute_ms = std::chrono::duration<double, std::milli>(end - start).count();
        engine::core::read_tensor_f32_into(output.tensor, result.values);
        return result;
    }
};