test_runner: fix diagnostics channel context tracking

[MoLow]

No description provided.

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73416/

[codecov]

Codecov Report

❌ Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.06%. Comparing base (131fd84) to head (fa0a640).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/test_runner/test.js	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63283      +/-   ##
==========================================
- Coverage   91.94%   90.06%   -1.89%     
==========================================
  Files         362      714     +352     
  Lines      155999   225251   +69252     
  Branches    24057    42583   +18526     
==========================================
+ Hits       143429   202864   +59435     
- Misses      12295    14171    +1876     
- Partials      275     8216    +7941     

Files with missing lines	Coverage Δ
lib/internal/test_runner/test.js	97.00% <95.00%> (+0.06%)	⬆️

... and 477 files with indirect coverage changes

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