Move water use data structure to a dataclass

[timothy-nunn]

Moves the water_use_variables.py global variables into a dataclass and provides the infrastructure for managing this new way of managing data.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.35632% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.64%. Comparing base (0f65c5e) to head (dd6d4b2).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
process/main.py	57.14%	6 Missing ⚠️
process/core/io/data_structure_dicts.py	0.00%	2 Missing ⚠️
process/core/caller.py	0.00%	1 Missing ⚠️
process/core/output.py	0.00%	1 Missing ⚠️
process/models/water_use.py	95.45%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4120      +/-   ##
==========================================
+ Coverage   47.30%   47.64%   +0.34%     
==========================================
  Files         140      143       +3     
  Lines       29448    29986     +538     
==========================================
+ Hits        13929    14286     +357     
- Misses      15519    15700     +181     

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[je-cook]

I think this looks good as a half way house (excluding the known shittyness). A couple of comments on the tests