Wrap RotatingStar to be usable in GhValenciaDivClean

[ncorsobh]

Proposed changes

Adds the RelativisticEuler solution for RotatingStar to the list of WrappedGR solutions usable in GhValenciaDivClean. Adds time derivatives to the solution (all of which identically 0) to allow it to be compatible with this function.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[nilsdeppe]

Thanks for doing this! You can squash and rebase immediately

[nilsdeppe]

CI failure is unrelated to this PR