Many race conditions on published messages data

[VRichardJP]

For example, let's focus on this->imu_stamp:

Its value is set in callbackImu here:

direct_lidar_inertial_odometry/src/dlio/odom.cc

Line 866 in bed8ae3

this->imu_stamp = imu->header.stamp;

And then it is used as timestamp for published messages in the following callbacks:

• in publishPose (timer callback)
• in callbackCloud (lidar sensor data callback)

Since everything runs in parallel in multiple thread, you get a race condition. For example, by the time the latest LIDAR scan has been processed and is ready to be published, many IMU messages may have been received already, thus causing the published LIDAR stamp look further in time than it actually is.

The consequence is that some of the data DLIO publishes is not reliable.