fix: Adding support for quadratic functions using the table data parser

[pesap]

Currently only works for heat rate and not cost curves.

Implementation details:

• Added new fields for generators to capture quadratic heat rate curve. For simplicity, the names are heat_rate_a0, heat_rate_a1, heat_rate_a2. All of the new fields are null by default. Open to suggestions on the nameing,
• If any heat_rate_a* column are defined, then we call create_poly_cost for ThermalGen,
• create_poly_cost will return
  • QuadraticCostCurve if all the coefficients are passed
  • LinearCurve if a1 and a0 is passed,
  • LinearCurve if a1 is passed,.
  • raise an Error if a2 is passed but a1 or a0 is nothing,

Closes #1177

[codecov]

Codecov Report

Attention: Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.55%. Comparing base (4b2c01b) to head (319f8a9).
Report is 2 commits behind head on main.

Files	Patch %	Lines
src/parsers/power_system_table_data.jl	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1178      +/-   ##
==========================================
+ Coverage   84.52%   84.55%   +0.02%     
==========================================
  Files         179      179              
  Lines        8169     8188      +19     
==========================================
+ Hits         6905     6923      +18     
- Misses       1264     1265       +1     

Flag	Coverage Δ
unittests	84.55% <95.23%> (+0.02%)	⬆️

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Files	Coverage Δ
src/PowerSystems.jl	100.00% <ø> (ø)
src/parsers/power_system_table_data.jl	82.36% <95.23%> (+0.35%)	⬆️

[rodrigomha]

Remove or update the warnings and update briefly the docs

[pesap]

Remove or update the warnings and update briefly the docs

This has been addressed.

[GabrielKS]

Looks good aside from the typo