[OdometryPublisher] Include Gaussian noise in pose messages

[pariaspe]

Desired behavior

Following the odometry publisher plugin description, both pose and twist messages should be noisy but only the twist has noise. (Notice the blue point in the graph corresponding the model pose).

Alternatives considered

Checking the source code, pose in odometry message is built directly getting the model pose in world:

gz-sim/src/systems/odometry_publisher/OdometryPublisher.cc

Lines 358 to 366 in 990f1c2

	// Get and set robotBaseFrame to odom transformation.
	//! [worldPose]
	const math::Pose3d rawPose = worldPose(this->model.Entity(), _ecm);
	//! [worldPose]
	//! [setPoseMsg]
	math::Pose3d pose = rawPose * this->offset;
	msg.mutable_pose()->mutable_position()->set_x(pose.Pos().X());
	msg.mutable_pose()->mutable_position()->set_y(pose.Pos().Y());
	msgs::Set(msg.mutable_pose()->mutable_orientation(), pose.Rot());

Implementation suggestion

I guess the better way to do it to integrate noisy velocity to get pose with some drift.

Additional context

I used Gazebo Sim, version 8.3.0, installed by binaries. But, I copied OdometryPublisher from gz-sim9 branch and compiled it manually.