Rework Pilz' unittests and remove PBRT from moveit_resources

[rhaschke]

That's a replacement for #2653. I summarize the main outcomes here:

• We have a circular dependency when building moveit_resources as an upstream for MoveIt
• To resolve this issue for now, we kept moveit_resources as part of the target workspace:
  https://github.com/ros-planning/moveit/blob/8992f16a779391fbac1c9720bd30d6bbb9d66760/.github/workflows/ci.yaml#L33
• Pilz stopped the production of their PBRT robot: Failing Pilz unit test due to circular dependency #2653 (comment)
• Thus, we should remove PBRT from moveit_resources in the long run
• Having a deterministic, analytical solver for the Pilz unit tests is important though.
  Thus, we decided to use the moveit_opw_plugin for the Fanuc robot in moveit_resources.
  • Migrate moveit_opw_plugin to moveit_kinematics #2746
• It remains to migrate all Pilz unit tests to this robot setup