JP-2013 NIRSpec leakcal and nodded exposures

[jemorrison]

Resolves JP-2013

Closes #5911

This PR follows changes made in how level-2b associations are created for NIRSpec exposures with both leakcal and nodded exposures (#7405). The calspec2 pipeline has been changed to subtract leakcal images from science and background data before the background step is run on the science data.

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]: results

https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/534/

• Make sure the JIRA ticket is resolved properly

[jemorrison]

Running regressions tests now

[codecov]

Codecov Report

Base: 78.61% // Head: 78.51% // Decreases project coverage by -0.10% ⚠️

Coverage data is based on head (355b92c) compared to base (d89abc0).
Patch coverage: 59.25% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7426      +/-   ##
==========================================
- Coverage   78.61%   78.51%   -0.11%     
==========================================
  Files         455      455              
  Lines       39143    39211      +68     
==========================================
+ Hits        30773    30787      +14     
- Misses       8370     8424      +54     

Flag	Coverage Δ
nightly	78.59% <59.25%> (-0.02%)	⬇️
unit	51.41% <40.74%> (+0.06%)	⬆️

Impacted Files	Coverage Δ
jwst/imprint/imprint_step.py	70.96% <52.63%> (-29.04%)	⬇️
jwst/pipeline/calwebb_spec2.py	94.20% <75.00%> (+0.06%)	⬆️
jwst/wfss_contam/observations.py	47.36% <0.00%> (-10.41%)	⬇️
jwst/regtest/regtestdata.py	86.23% <0.00%> (-0.46%)	⬇️

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[jemorrison]

The regression test show 8 failures. 4 failures are from tests that has an extra keyword S_IMPRINT SKIPPED.
In those 4 causes the imprint step should not be run because the data is not NIRSPEC IFU data. I am not sure why the S_IMPRINT was not set to SKIP before. I down loaded on of the test data: test_miri_lrs_slit_spec. I ran calspec2 on the data and by default the IMPRINT step is set to skip. Now it is written in the header and before it was not. Maybe something else changes to does this now ?
The 4 other tests are related to NIRISS SOSS and I do not think are related to this PR.

[jemorrison]

I re-ran the regression tests and now there are only 4 "failures" - these are just 1 difference in header that now has the IMPRINT step set to skipped. In these cases it should be set to skipped because the data is not NIRSpec IFU data

[stscieisenhamer]

LGTM.