prefer moveit::core over robot_state namespace

[v4hn]

Confusingly, robot_model/robot_model.h creates alias namespaces for moveit::core. Ioan added this long ago to stay backward compatible with old usage.

However, as a result the namespaces where not aligned throughout the codebase (grep for robot_state::RobotState, for example) and the alias is still there.

I believe we should deprecate the old names and align our codebases not to use the old names.

@davetcoleman

[davetcoleman]

This duplicate namespacing has always bothered me. @v4hn why did you close this? How about we make the change now in MoveIt 2? @henningkayser

[rhaschke]

Actually, most of these namespace instances were removed in #1924. But there are still a few left...

[v4hn]

I was under the impression the linked pr fixed it, but @rhaschke is right, apparently there are still some places left..

[v4hn]

pr will be ready in 25 😇