Use point cloud transport to allow compressed point clouds

[kbrameld]

Replaces the publisher in pointcloud_filter.cpp with a point_cloud_transport publisher. point_cloud_transport is similar to image_transport, and makes topics available for each installed point_cloud_transport plugin.

RViz uses point_cloud_transport too and with these changes, it is possible to compress / decompress point clouds efficiently without the need for separate compression / decompression nodes. In RViz, you need to manually enter the "/zstd" topic suffix (if using zstd plugin), as the compressed transports don't show up in the drop down automatically.

[sysrsbuild]

Can one of the admins verify this patch?

[Nir-Az]

Hi, thanks for the PR.
Some questions?

Does it relates to image_transport package?
Does it support intra_process configuration or it needs to be disabled on such like in image_transport?

Will it be triggered to work if the package is installed and if not will work as the normal topic? like in image_transfer?

We need to be back compatable or to add this as an extra feature the user can turn on