public long getGracefulShutdownQuietPeriodMillis() {
        return gracefulShutdownQuietPeriodMillis;
    }
Returns the number of milliseconds to wait for active requests to go end before shutting down.

@see #getGracefulShutdownTimeoutMillis()
@see ServerBuilder#gracefulShutdownTimeout(Duration, Duration)
spring/boot3-autoconfigure/src/main/java/com/linecorp/armeria/spring/ArmeriaSettings.java