Create datum setter node for robot_localization launch

[AbBaSaMo]

When the pkg is launched, we need to set the datum via a service. So we'll need a node that reads gps values and calls this service ONCE and in ENU standard where a 0 heading is east

Originally posted by @AbBaSaMo in #19

[AbBaSaMo]

SetDatum is a service defined in the robot_localization package https://github.com/Monash-Connected-Autonomous-Vehicle/robot_localization/blob/humble-devel/srv/SetDatum.srv

It requires a message of type GeoPose https://docs.ros.org/en/noetic/api/geographic_msgs/html/msg/GeoPose.html which contains the following:

• GeoPoint position = {lat, long, alt} obtained from navsatfix
• Quaternion orientation = {x, y, z, w} which idk where to get this from as nothing from the piksi provides this

https://answers.ros.org/question/237947/how-do-you-use-the-navsat_transform-set_datum-service/ suggests using 0 0 0 1 minimally for orientation

Will also have to look into the stuff docs mentioned about ensuring imu abides by standards

[AbBaSaMo]

0 0 0 1 orientation means the robot has a neutral orientation with no rotations, so it seems this is why it is suggested as a starting orientation

[AbBaSaMo]

It appears to be working with the set datum as the co-ords of clayton VIC

[AbBaSaMo]

I misread the docs/tutes on robot_loc. It seems if we set the wait_for_datum parameter as false, the package does not require us to set an initial datum. Everything works even when the datum setter node is not running. If the param is true otherwise, we set the datum as an origin point

Will leave the implementation just in case we decide for whatever reason to set this param as true but closing the issue now.