ci: set ulimit -c unlimited for gitlab tests (#11400)

## Checklist
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## Reviewer Checklist
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- Testing strategy adequately addresses listed risks
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[release branch maintenance
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.gitlab/testrunner.yml

@@ -4,5 +4,6 @@
   tags: [ "arch:amd64" ]
   timeout: 20m
   before_script:
+    - ulimit -c unlimited
     - pyenv global 3.12 3.7 3.8 3.9 3.10 3.11 3.13-dev
     - export _CI_DD_AGENT_URL=http://${HOST_IP}:8126/