Update upload-artifact action to version 4 in buildtest workflow

[tg123]

https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

also fix e2e tests flaky

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@@            Coverage Diff            @@
##             master    #1615   +/-   ##
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  Coverage          ?   70.64%           
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  Files             ?       89           
  Lines             ?     2681           
  Branches          ?      557           
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  Hits              ?     1894           
  Misses            ?      787           
  Partials          ?        0           

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[brendandburns]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: brendandburns, tg123

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