[Infra] Fix flaky tests

[martincostello]

Changes

Fix flaky tests found in recent CI jobs.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.67%. Comparing base (01b9df7) to head (1243e3e).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7400      +/-   ##
==========================================
+ Coverage   89.64%   89.67%   +0.03%     
==========================================
  Files         276      276              
  Lines       14576    14576              
==========================================
+ Hits        13066    13071       +5     
+ Misses       1510     1505       -5     

Flag	Coverage Δ
unittests-Project-Experimental	89.63% <ø> (+0.08%)	⬆️
unittests-Project-Stable	89.62% <ø> (+0.01%)	⬆️

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see 2 files with indirect coverage changes

[martincostello]

Three runs where the only failures were timeouts caused by coverage upload (investigating that separately).