Update DKRZ Recipe Test Workflow to the use <site>-recipes.cylc

[chrisbillowsMO]

For DKRZ, a dkrz-recipes.cylc needs to created DKRZ's RTW configurations migrated.

This is because the configuration for the RTW was changed in #3724/#3856

• Recipes are no longer listed in the flow.cylc file
• Custom recipe directives are no longer stores in the <site>.cylc file
• Instead both recipes AND directives are stored in a site specific recipes.cylc file in the site/ directory

See the ESMValTool/RTW documentation for more information.

(See also the same ticket for JASMIN: #3858 )

• When done, add a link to the dkrz-recipes.cylc to RTW Currently Test Recipes