Automate the process for generating structs

[daniel-thom]

This is the PSY corollary to https://github.com/NREL-SIIP/InfrastructureSystems.jl/pull/293.

[jd-lara]

Can you update the the Project toml to IS 1.18 to re-run test?

[codecov[bot]]

Codecov Report

Merging #917 (11f576a) into master (9f637cb) will decrease coverage by 0.01%. The diff coverage is 75.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #917      +/-   ##
==========================================
- Coverage   88.95%   88.94%   -0.02%     
==========================================
  Files         158      159       +1     
  Lines        7562     7570       +8     
==========================================
+ Hits         6727     6733       +6     
- Misses        835      837       +2     

Flag	Coverage Δ
unittests	88.94% <75.00%> (-0.02%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/utils/generate_struct_files.jl	75.00% <75.00%> (ø)

[jd-lara]

This MR looks good but it seems that an unrelated change to JSON3 broke the tests