chore: Minor test fixes

[dpogue]

Platforms affected

None

Motivation and Context

Resolves some deprecations warnings printed to the console in Node 22.

Description

• The fs.Stats constructor is deprecated in Node 22 and prints a warning to the console, so we want to find a way to avoid hitting that
• We got some warnings elsewhere that temporary files weren't cleaned up properly after test runs. Try using the tmp npm module to handle this better

Testing

Ran unit tests locally on Node 22.

Checklist

• [x] I've run the tests to see all new and existing tests pass

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.40%. Comparing base (3d7f736) to head (52b849a).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #211 +/- ## ======================================= Coverage 88.40% 88.40% ======================================= Files 20 20 Lines 1147 1147 ======================================= Hits 1014 1014 Misses 133 133 ```

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