Add CI to check for unhandled warnings in tests

[bhazelton]

Description

Check so that we don't accumulate unhandled warnings and new warnings do not go unnoticed.

Motivation and Context

closes #389

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Reference simulation update or replacement
• [ ] Documentation change (documentation changes only)
• [ ] Version change
• [x] Build or continuous integration change

Checklist:

For all pull requests:

• [x] I have read the contribution guide.
• [x] My code follows the code style of this project.

Build or continuous integration change checklist:

• [ ] If required or optional dependencies have changed (including version numbers), I have updated the readme to reflect this.
• [ ] If this is a new CI setup, I have added the associated badge to the readme and to references/make_index.py (if appropriate).

[codecov[bot]]

Codecov Report

Merging #391 (c1da2f4) into main (ca7ec44) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #391   +/-   ##
=======================================
  Coverage   99.33%   99.33%           
=======================================
  Files          13       13           
  Lines        2094     2094           
=======================================
  Hits         2080     2080           
  Misses         14       14           

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