Wind Energy not casting number arguments

[dcdenu4]

Rob G. reported in Slack that he and a colleague were experiencing issues with the wind energy model when trying to edit the foundation_cost in the Workbench UI. They were getting:

2024-01-03 21:09:01,050 (natcap.invest.wind_energy) wind_energy._calculate_npv_levelized_rasters(1357) INFO Creating output NPV and levelized rasters.
2024-01-03 21:09:01,063 (taskgraph.Task) Task.add_task(706) ERROR Something went wrong when adding task calculate_npv_levelized_rasters (18), terminating taskgraph.
Traceback (most recent call last):
  File "taskgraph\Task.py", line 674, in add_task
  File "taskgraph\Task.py", line 1093, in _call
  File "natcap\invest\wind_energy.py", line 1415, in _calculate_npv_levelized_rasters
TypeError: can only concatenate str (not "float") to str

It turns out that the wind energy model passes all of args into _calculate_npv_levelized_rasters and does not do any casting on the number fields it uses from args.