JP-2035: Ramp fit ols gls sep

[kmacdonald-stsci]

Closes #5943

Resolves JP-2035

Description

This PR separates the OLS and GLS algorithms to their own files, instead of both in the one ramp_fit.py file.

Checklist

• Tests
• Documentation
• Change log
• Milestone
• Label(s)

[codecov]

Codecov Report

Merging #5951 (5f2bb30) into master (c5cfcd5) will increase coverage by 0.19%.
The diff coverage is 61.67%.

@@            Coverage Diff             @@
##           master    #5951      +/-   ##
==========================================
+ Coverage   77.91%   78.10%   +0.19%     
==========================================
  Files         403      404       +1     
  Lines       35359    37038    +1679     
==========================================
+ Hits        27549    28929    +1380     
- Misses       7810     8109     +299     

Flag	Coverage Δ		*Carryforward flag
nightly	77.91% <63.52%> (ø)		Carriedforward from e41f568
unit	56.06% <54.58%> (+0.02%)	⬆️

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
jwst/ramp_fitting/ols_fit.py	82.89% <ø> (ø)
jwst/ramp_fitting/ramp_fit.py	77.53% <ø> (+0.21%)	⬆️
jwst/ramp_fitting/gls_fit.py	68.24% <59.49%> (-2.04%)	⬇️
jwst/ramp_fitting/utils.py	96.41% <75.67%> (-0.20%)	⬇️
jwst/resample/resample_spec_step.py	90.51% <0.00%> (-4.67%)	⬇️
jwst/associations/lib/rules_level2b.py	93.84% <0.00%> (-2.87%)	⬇️
jwst/associations/lib/rules_level3.py	98.75% <0.00%> (-0.49%)	⬇️
... and 1 more

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[dmggh]

This segregation of OLS and GLS code is an improvement, and will make it easier to maintain the code. In a later PR, refactoring fit_next_segment() should help reduce the size of the new module ols_fit.py, where the OLS-specific functions now live. Don't forget to update the change log.

[hbushouse]

LGTM