Some functions in sll has no namespace but too generic names

[EmilyBourne]

Ie., the function save_logger() here:

https://gitlab.maisondelasimulation.fr/gysela-developpers/gyselalibxx/-/blob/main/vendor/sll/include/sll/matrix_utils.hpp?ref_type=heads#L89

Has no namespace and is thus exposed to all classes using the MatrixBatchEll/Csr classes (ie. Poisson-related classes). The name being generic, it would be in conflict with any function sharing the same name.

Several solutions:

• Use more specialized names (like matrix_batch_save_logger...)
• Add a namespace to Matrix classes (just MatrixBatchEll/Csr, other SLL matrices being planned to be removed, see #293 )\n\n__Issue originally opened by @blegouix on GitLab__