Fix ZO costing method documentation

[bknueven]

Fixes: #1064

Summary/Motivation:

See #1064.

Changes proposed in this PR:

• Update ZO rst file creator to dynamically write the location of ZO unit costing methods and re-factor of the rst file creator so its functions can be called in isolation (79e85fe)
• Update resulting rst files (8172548)
• Drive-by bug fix for costing, or lack thereof, on FeedZO and GasSpargedMembraneZO (888f363)

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[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 95.53%. Comparing base (98aa405) to head (661de05).
Report is 271 commits behind head on main.

Files	Patch %	Lines
watertap/unit_models/zero_order/feed_zo.py	66.66%	1 Missing ⚠️
.../unit_models/zero_order/gas_sparged_membrane_zo.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1081      +/-   ##
==========================================
- Coverage   95.53%   95.53%   -0.01%     
==========================================
  Files         318      318              
  Lines       30991    30997       +6     
==========================================
+ Hits        29608    29612       +4     
- Misses       1383     1385       +2     

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[adam-a-a]

From a quick skim, I am guessing that most of the modifications in this file had to do with (1) moving the bulk of the code under this conditional used for script execution and (2) revising conditionals for feed_zo since you added something to the unit model to account for lack of costing. Any other major changes that I missed (or misconstrued)?

[bknueven]

Besides the indentation, the only thing that has really changed is now the name and path of the costing method is pulled directly off the unit model class by checking its default_costing_method attribute. See: https://github.com/bknueven/watertap/blob/79e85fea9bda3b969ed03a65a2677f01f26842c4/docs/technical_reference/unit_models/zero_order_unit_models/automate_rst_file_wt3.py#L382-L392

So in the Excel sheet now the costing_method column really means "does this unit have costing?".

[adam-a-a]

Small thing, but I realized that "SMP" is not capitalized in the toc tree nor within the rst file. To change this, you can add an entry for smp in title_exceptions in the automation script. I remember some talk about removing this unit all together, but since we have it here, might as well give it a name. @kurbansitterley do you remember what "SMP" stood for in WT3?

[kurbansitterley]

Hm no I don't remember... soluble microbial products is the only SMP acronym I know.

[bknueven]

WT3 doesn't seem to know either.. https://github.com/search?q=repo%3ANREL%2FWaterTAP3%20SMP&type=code

[bknueven]

I elected to just capitalize SMP 3de7d0f