Set DQ of ref pixels to DO_NOT_USE after refpix correction

[jdavies-st]

Closes #7015

This PR addresses the current fragility of how reference pixels are set to DO_NOT_USE in calwebb_detector1. Currently they rely on the GAIN reference file having zeros in the reference pixel locations, and then ramp_fitting sets those pixels to DO_NOT_USE in the science data DQ.

This PR sets the DQ of reference pixels to DO_NOT_USE at the end of the refpix step. It does require that DQInitStep label these properly as REFERENCE_PIXELS, but this seems to be the case currently for the currently selected MASK reference files for all instruments.

Is this the best way to do this? Thoughts?

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

Base: 78.60% // Head: 78.71% // Increases project coverage by +0.11% 🎉

Coverage data is based on head (21fd546) compared to base (e2284d1).
Patch coverage: 94.73% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7017      +/-   ##
==========================================
+ Coverage   78.60%   78.71%   +0.11%     
==========================================
  Files         455      455              
  Lines       39148    39431     +283     
==========================================
+ Hits        30771    31039     +268     
- Misses       8377     8392      +15     

Flag	Coverage Δ		*Carryforward flag
nightly	78.59% <92.85%> (ø)		Carriedforward from e2284d1
unit	51.41% <85.71%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
jwst/refpix/reference_pixels.py	93.36% <94.73%> (+0.54%)	⬆️

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[zacharyburnett]

Suggested change

	refpix
	------
	- Set DQ of ref pixels to DO_NOT_USE after `refpix` correction [#7017]

now that #8671 is merged (switching change log handling to towncrier) this change log entry should be a file in changes/ instead:

echo "Set DQ of ref pixels to ``DO_NOT_USE`` after ``refpix`` correction" > changes/7017.refpix.rst

(new PRs will include instructions on how to do this)

[zacharyburnett]

(ignore this if this PR is no longer active or needed)