spectral extraction: background median vs average dropdown

[kecnry]

Description

This pull request provides a dropdown to choose between median and average for the background statistic passed to specreduce.

Screen.Recording.2022-12-14.at.12.41.09.PM.mov

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a milestone set? Set this to bugfix milestone if this is a bug fix and needs to be released ASAP; otherwise, set this to the next major release milestone.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Base: 88.48% // Head: 88.49% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (e57350c) compared to base (46f0ae2).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1922   +/-   ##
=======================================
  Coverage   88.48%   88.49%           
=======================================
  Files          95       95           
  Lines       10616    10619    +3     
=======================================
+ Hits         9394     9397    +3     
  Misses       1222     1222           

Impacted Files	Coverage Δ
...plugins/spectral_extraction/spectral_extraction.py	91.36% <100.00%> (+0.06%)	⬆️

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[javerbukh]

I'm still seeing the "1" error message pop up first, is that a blocker for this PR? Also, the first time I ran the Specviz2D notebook, I saw 329 console messages similar to "WARNING:Comm:No such comm: 128d1ae6350540aea927dff79ec56c23", but when I re-ran the notebook a few more times I did not see that. Not sure what that's about but I figured I'd mention it. If the "1" message is not a blocker, I'll go ahead and approve.

[kecnry]

The "1" is #1888 and not affected or caused by this PR. I think someone else has seen the comm issue - if there isn't already a ticket tracking that maybe there should be (but definitely not related to this PR).

[rosteen]

LGTM, I can see that the extracted spectrum changes slightly depending on which background statistic I pick.