Migration to the new CI

[gilles-peskine-arm]

This issue lists things that we need to do to fully migrate to the new CI.

• Confirm that the new release CI job has feature parity to the internal release testing job.
• Test the new release CI job and confirm that we can make an emergency release if needed

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• Trial period where the new CI runs in parallel with the old one on pull request and nightlies
• Have a name that isn't “new CI”
  • Current plan: switch the new CI to the existing name ("TF OpenCI: PR tests" and "TF OpenCI: Interface stability tests"), and switch the Linaro CI to a different name "TF OpenCI (legacy): PR tests" and "TF OpenCI (legacy): Interface stability tests".
• Adapt Groovy scripts → CI script changes needed for the New CI #218
• Update developer guide
• Update Arm internal documentation
• Adapt mbedtls-kick-ci → mbedtls-kick-ci: switch to the new OpenCI instance mbedtls-docs#190
• Adapt CI stats (health) script from @mpg
• Switch the required check all protected branches from the current CI (Linaro OpenCI) to the new one
  • Switched to "New CI (testing): PR tests" on 2025-11-03 ~17:00
• Trial period where the new CI does the merge queues
• Switch the www.trustedfirmware.org test system dashboard
• Migrate the previous persistent release artifacts from the mbedtls-release-new