SF: trace vsyncPeriod from onComposerHalVsync

void SurfaceFlinger::onComposerHalVsync(hal::HWDisplayId hwcDisplayId, int64_t timestamp,

                                        std::optional<hal::VsyncPeriodNanos> vsyncPeriod) {

    ATRACE_CALL();

    const std::string tracePeriod = [vsyncPeriod]() {

        if (ATRACE_ENABLED() && vsyncPeriod) {

            std::stringstream ss;

            ss << "(" << *vsyncPeriod << ")";

            return ss.str();

        }

        return std::string();

    }();

    ATRACE_FORMAT("onComposerHalVsync%s", tracePeriod.c_str());

    Mutex::Autolock lock(mStateLock);

    const auto displayId = getHwComposer().toPhysicalDisplayId(hwcDisplayId);