Changes

pipelines(qa): migrate fileserver.pingcap.net artifacts to OCI registry (#4302)

- [x] Migrate `pipelines/qa/qa-release-br-integration-test.groovy` from
fileserver to OCI artifacts
- [x] Migrate
`pipelines/qa/qa-release-lightning-integration-test.groovy` from
fileserver to OCI artifacts
- [x] Remove commented-out fileserver URL from
`jenkins/pipelines/qa_release_test.groovy`
- [x] Remove 'Debug info' stage from both qa pipelines

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<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>fileserver: migrate artifacts for qa</issue_title>
> <issue_description>Replace fileserver.pingcap.net usage for qa with
OCI artifacts in a standard registry.
> 
> Acceptance criteria:
> - No fileserver.pingcap.net references in jobs/pipelines for qa
> - Artifacts pulled via OCI registry with documented paths
> </issue_description>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> </comments>
> 


</details>



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- Fixes PingCAP-QE/ci#4221

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wuhuizuo <2574558+wuhuizuo@users.noreply.github.com>
 (commit: 2e276f8)