Change robot types to include a namespace

[luca-della-vedova]

New feature implementation

Depends on open-rmf/rmf_traffic_editor#521.

Implemented feature

This PR changes the robot_spawn_type in demo maps to include an Open-RMF namespace, similar to how normal models have an OpenRobotics namespace. The relevant models (all except the RobotPlaceholder that is not used anymore as far as I can tell) have been uploaded to a new Open-RMF organization on the gazebosim portal.
This is to help in future-proofing the maps for the site editor.

Test it!

When doing a clean build with this branch and the matching rmf_traffic_editor branch, all demos should still work.

[luca-della-vedova]

Note that this change, together with uploading the TeleportIngestor and TeleportDispenser plugins to fuel, will make pit_crew download the models and there will be silently two of the same model in .gazebo/models as well as the rmf_demos installation folder.
The possible actions are either:

1. Remove the models from Fuel (Site editor won't be able to download it) or:
2. Remove the model from rmf_demos_assets and it will be downloaded by pit_crew (it's just a box with a plugin).
3. Keep as is and there might be ambigious lookup in Gazebo.

Option 3) is definitely not a good idea, 1) and 2) have different tradeoffs

[mxgrey]

Is gazebo only given the plain model name without the organization name to distinguish between them? And is gazebo not able to account for an organization name when searching for a model?

If yes to both then I imagine this is a broader problem that will need to be resolved within Gazebo or else it's going to cause trouble for large projects in general.

[luca-della-vedova]

Is gazebo only given the plain model name without the organization name to distinguish between them?

Yes. As part of the generation the organization name is removed here so OpenRobotics/Chair is translated into a bare model://Chair.

And is gazebo not able to account for an organization name when searching for a model?

It should definitely be possible if we specify models the "proper gazebo way", which is through Fuel URLs other than our own schema, like this.

I haven't looked into what happens if we remove the "organization stripping" logic from our world generation, but there are a few caveats:

• If it works as intended, we will need to change our model download pipeline to have subfolders for organizations (it currently doesn't).
• We will also need to change how we install models from rmf_demos_assets to be installed under an Open-RMF organization subfolder.
• If users have their own asset package (i.e. forked rmf_demos_assets) it will stop working unless they also update their folder structure.

Finally, the root of this specific issue is that the asset exists both on Fuel and rmf_demos_assets and that would persist. pit_crew has no knowledge of what models have been installed and sourced in the workspace so it can't detect that an Open-RMF/TeleportIngestor has been installed. It will only detect that the map has an Open-RMF/TeleportIngestor model and thus it should try downloading it.