common code for linearity correction

[cshanahan1]

Adds common code for linearity correction (WIP)

[codecov]

Codecov Report

Merging #55 (2d72add) into main (6b9ddd3) will increase coverage by 2.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   19.91%   21.99%   +2.08%     
==========================================
  Files          13       14       +1     
  Lines        1572     1614      +42     
==========================================
+ Hits          313      355      +42     
  Misses       1259     1259              

Impacted Files	Coverage Δ
src/stcal/linearity/linearity.py	100.00% <100.00%> (ø)

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[dmggh]

Looks good except for residual print statement.

[kmacdonald-stsci]

There are codecov comments saying the code isn't covered by tests. Is this code covered by the JWST tests or will those tests be moved to STCAL?

[nden]

The error in the jwst tests is understood and fixed in other PRs, awaiting release of stcal.
Merging this one.