chore(llc): fix test coverage

[renefloor]

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Description of the pull request

codecov was not reporting coverage of files that weren't tested. By changing this import at least all files that are somehow exposed in stream_core.dart are reported for coverage.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 18.01%. Comparing base (5dc4aa2) to head (516cac3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #15       +/-   ##
===========================================
- Coverage   87.05%   18.01%   -69.05%     
===========================================
  Files           4       47       +43     
  Lines         170      877      +707     
===========================================
+ Hits          148      158       +10     
- Misses         22      719      +697     

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