Unit test for median memory usage

[emolter]

This PR adds a unit test ensuring that the median calculation in outlier detection does not substantially exceed the expected amount as calculated from the input data size.

Relates to JP-3775 but only fixes one small part of that ticket.

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stcal@<branch>")
    • jwst regression test
    • romancal regression test

news fragment change types...

• changes/<PR#>.apichange.rst: change to public API
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.23%. Comparing base (5f94030) to head (d3459dd).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #299      +/-   ##
==========================================
+ Coverage   85.19%   85.23%   +0.03%     
==========================================
  Files          46       46              
  Lines        8804     8823      +19     
==========================================
+ Hits         7501     7520      +19     
  Misses       1303     1303              

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