[build-tools] upload serve-sim metrics artifact on session teardown

[gwdp]

Why

so a finished simulator session's CPU/memory shows up in the dashboard (the live stream is gone once the session ends).

How

at session teardown, lists serve-sim's /artifacts, downloads the metrics NDJSON, and uploads it through the same uploadDeviceRunSessionArtifactAsync path as other session artifacts. the file grows all session, so it's fetched once at the end rather than mid-session.

Test Plan

CI passes. unit tests cover listing, download+upload, and the teardown drain.

[gwdp]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [build-tools] upload serve-sim metrics artifact on session teardown #3995 👈 (View in Graphite)
• [build-tools] pass metrics CORS origin to serve-sim #3990
• main

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[github-actions]

✅ Thank you for adding the changelog entry!

[codecov]

Codecov Report

❌ Patch coverage is 85.48387% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.65%. Comparing base (1230799) to head (158b437).

Files with missing lines	Patch %	Lines
...s/build-tools/src/steps/utils/serveSimArtifacts.ts	89.66%	6 Missing ⚠️
.../src/steps/functions/startServeSimRemoteSession.ts	25.00%	3 Missing ⚠️

Additional details and impacted files

@@                       Coverage Diff                       @@
##           gwdp/serve-sim-metrics-cors    #3995      +/-   ##
===============================================================
- Coverage                        59.80%   59.65%   -0.15%     
===============================================================
  Files                              936      939       +3     
  Lines                            41069    41299     +230     
  Branches                          8639     8688      +49     
===============================================================
+ Hits                             24559    24632      +73     
- Misses                           16416    16573     +157     
  Partials                            94       94              

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