Remove Pose2D deprecation warning and retain it

Hi,

I know this discussion has come up before, but it has once more come to my attention that Pose2D is an important message type which is used widely and has value in readability and conciseness for the mobile robot use-case. While I do not generally support using it internally within Nav2 because I'd like to be as agnostic as possible, there are many situations where it is used for specialized purposes and has significant value in existence.

More than representing SE2 poses in the navigation context, it is also useful for image processing like in vision_msgs where having 3 axis rotations are not meaningful for image plane analysis of results.

Finally, while not a strong argument on its own, it seems odd to depreciate the message in ROS 1 given it won't be removed from any existing OS, it was still included in Noetic, and there will not be another one. The commit message for this deprecation warning says that it is for forward porting it, but its forward porting something that will never actually be removed in the initial location.

Start by reviewing the Pose2D definition and the prior discussion referenced in this issue, including how its deprecation warning is represented in the common interface packages. Compare the ROS 1 and ROS 2 handling described here, then determine the maintainers' intended outcome before proposing changes; the issue does not name a file, test, or acceptance criterion.