Add plots for wastewater concentrations

[sbidari]

Adds plots of wastewater concentration to the postprocessing steps.

Summary of changes:

• preprocessing of wastewater data to ensure lab_site_index ordered by population size
• Updates process_state_forecast.R, make_forecast_figure.R and plot_and_save_state_forecast.R to handle new variables
• Adds NWSS data and associated variable column lab_site_index to pipelines/prep_data.py
• Update pipelines/score_forecast.R and pipelines/timeseries_forecast.R to handle lab_site_index column appropriately

[codecov]

Codecov Report

Attention: Patch coverage is 8.00000% with 92 lines in your changes missing coverage. Please review.

Project coverage is 30.16%. Comparing base (6b4f986) to head (f16acd1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
hewr/R/process_state_forecast.R	8.97%	71 Missing ⚠️
hewr/R/make_forecast_figure.R	0.00%	11 Missing ⚠️
pipelines/prep_data.py	20.00%	4 Missing ⚠️
pyrenew_hew/pyrenew_hew_model.py	0.00%	3 Missing ⚠️
hewr/R/directory_utils.R	0.00%	2 Missing ⚠️
pipelines/prep_eval_data.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #382      +/-   ##
==========================================
- Coverage   30.58%   30.16%   -0.43%     
==========================================
  Files          26       26              
  Lines        1942     1986      +44     
==========================================
+ Hits          594      599       +5     
- Misses       1348     1387      +39     

Flag	Coverage Δ
hewr	34.02% <7.69%> (-1.53%)	⬇️
pipelines	14.35% <16.66%> (ø)
pyrenew_hew	42.24% <0.00%> (-0.07%)	⬇️

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[damonbayer]

Thanks @sbidari! Some changes requested.

[damonbayer]

Thanks @sbidari! I tried some minor modifications to clean up the plot saving, but I was unsuccessful. Going to save it for #388