[mascaret] Ambiguity in variable naming

Summary

Navigating variable names in Mascaret is currently quite challenging due to ambiguities related to:

• The type of mesh involved: cell-centered, interface, or offset,
• Spatial references such as left/right or upstream/downstream, which can be unclear or inconsistent.

This often makes it difficult to interpret variables correctly.

How to implement it?

A more structured approach could help. For example, introduce clearly defined objects or modules for each mesh type. Each of these objects could encapsulate spatial variables.