Concept for shared dimensions

Develop a concept for sharing dimension information across DataArray entities: At the moment each DataArray has its own dimension descriptors. Since this information is often repeated in many scenarios, it would be beneficial to share this information.

Start by reviewing how DataArray entities currently store their dimension descriptors. Define the scope and acceptance criteria for sharing repeated dimension information across DataArray entities; the issue does not identify files, tests, or a concrete implementation target.

Written by the indexing model from the issue text.