SWY: Monthly outputs should have consistent naming conventions

[megannissel]

The SWY model has many raster outputs that reflect monthly values. Some of these are named using a 1-indexed convention, so that the numbers align with month indices (1=January [...] 12=December). Others, however, are 0-indexed. These are generally the aligned versions of model inputs, but even so, the lack of consistency is a bit confusing and makes the model code less straightforward. It would be helpful if all files generated by the model followed the same naming convention, where numbers correspond to month indices.

[megannissel]

I am also planning to address this as part of the model updates in support of #2439

[claire-simpson]

Is the inconsistency independent of how the input files are provided? This PR, where support for zero-padded monthly input files was added: #1697, may be relevant

[megannissel]

Thanks, @claire-simpson! This inconsistency is strictly with output filenames, which are independent of the input filenames. I believe the model no longer cares about the names of the input monthly rasters, since those are now passed to the model by way of a CSV mapping month indices to file paths (see #2126).

[claire-simpson]

Thanks for the context! Seems like a good thing to standardize!