Method current_ms

tests/BS_thread_pool_test.cpp:3436–3439

* @brief Get the number of milliseconds that have elapsed since the object was constructed or since `start()` was last called, but keep the timer ticking. * * @return The number of milliseconds. */

     * @return The number of milliseconds.
     */
    [[nodiscard]] std::chrono::milliseconds::rep current_ms() const
    {
        return (std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - start_time)).count();
    }

    /**
     * @brief Start (or restart) measuring time. Note that the timer starts ticking as soon as the object is created, so this is only necessary if we want to restart the clock later.