SWY: Update output units and `created_if` conditions in model spec

[megannissel]

While working on the SWY report, we received requests from some of the model maintainers to update the units on several of the outputs to reflect the temporal dimension of the raster units. Since the model produces some outputs in mm/month and others in mm/year, accurately reflecting this in the units is helpful for users.

I also noticed that several of the outputs (both intermediate and main) lacked accurate created_if conditions. Many outputs, including those related to quickflow and precipitation, are only produced when user_defined_local_recharge=False. The model spec should be updated to reflect this.

[megannissel]

I'm tackling this as part of #2439, but thought it might be helpful to have a dedicated Issue tracking this aspect of the SWY updates!