JP-3009: Add cleanups for files left behind while running tests

[WilliamJamieson]

Resolves JP-3009

Closes #7128

This PR adds fixtures to a few tests so that those tests do not leave files generated and saved while running the tests behind. The unit tests for JWST should not leave behind "artifacts" after running as this could interfere with re-running tests and/or lead to those files accidentally being picked up by git.

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: 79.68% // Head: 79.68% // No change to project coverage 👍

Coverage data is based on head (8ca6c9a) compared to base (e85589c).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7375   +/-   ##
=======================================
  Coverage   79.68%   79.68%           
=======================================
  Files         412      412           
  Lines       37576    37576           
=======================================
  Hits        29944    29944           
  Misses       7632     7632           

Flag	Coverage Δ		*Carryforward flag
nightly	79.67% <ø> (ø)		Carriedforward from e85589c
unit	52.23% <ø> (ø)

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

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[hbushouse]

Is this essentially a fix for JP-3009, or does this only cover a subset of tests with this problem?

[WilliamJamieson]

Is this essentially a fix for JP-3009, or does this only cover a subset of tests with this problem?

Didn't know at all about JP-3009, I just noticed this while locally testing #7376 and it bothered me. I believe this does in fact resolve JP-3009! (Feel free to assign it to me if you want)