Add cross-platform CI with conda packages (minimal version)

[Tobias-Fischer]

Description

This PR supersedes #1600 and introduces cross-platform CI for rviz using the RoboStack. It is a minimal set of changes, in particular it does not include changes from #1532 that should be discussed separately. It would be great to get some feedback from the rviz maintainers to see whether there is interest in getting this merged :)

/cc @wolfv

Checklist

• If you are addressing rendering issues, please provide:
  • Images of both, broken and fixed renderings.
  • Source code to reproduce the issue, e.g. a YAML or rosbag file with a MarkerArray msg.
• If you are changing GUI, please include screenshots showing how things looked before and after.
• Choose the proper target branch: latest release branch, for non-ABI-breaking changes, future release branch otherwise.
  Due to the lack of active maintainers, we cannot provide support for older release branches anymore.
• Did you change how RViz works? Added new functionality? Do not forget to update the tutorials and/or documentation on the ROS wiki
• While waiting for someone to review your request, please consider reviewing another open pull request to support the maintainers of RViz. Refer to the RViz Wiki for reviewing guidelines.

[rhaschke]

Sorry for ignoring this PR for so long. I didn't have time to look into this yet.
Of course, I'm open to increase cross-platform compatibility and I agree to most of the changes here. However, I'm not sure we should establish a separate CI workflow. In MoveIt we experienced many false-positive alarms. So if you insist in this approach, please ensure that you fix all upstream dependencies to not experience false alarms.

[wolfv]

Ok, that was definitely too early for me :) sorry. I should boot on Windows and see what's going on here.

[rhaschke]

A few more comments 😉

[Tobias-Fischer]

I just merged noetic-devel into the cross-ci branch and have already picked up (and fixed) the first regression: 9b1f9dd

[rhaschke]

Finally, some remarks to the workflow definition. Please rename some files:

• .github/ci_cross_platform_env.yml -> .github/robostack_env.yaml
• .github/workflows/cross_platform_ci.yml -> .github/workflows/robostack.yaml
• .github/workflows/prerelease.yml -> .github/workflows/prerelease.yaml

Fix as many versions as possible to reduce the risk of false-positives.