fix(ci): prefer VPC mirror on ARC runners

[kongche-jbw]

Summary

• Prefer mirrors.cloud.aliyuncs.com for ARC/ECS Alinux jobs.
• Fall back to public mirrors.aliyun.com after two failed VPC mirror attempts.
• Pre-import the Alinux GPG key before dnf install to avoid late transaction failures.
• Keep GitHub-hosted manual runs on the public mirror.

Validation

• git diff --check
• YAML parse check for updated workflows

[kongche-jbw]

Verified on the ARC runner that the workflow now uses the VPC mirror instead of the public mirror.

Evidence from the latest run:

• Job: https://github.com/alibaba/anolisa/actions/runs/28985058137/job/86012133929?pr=1409
• Runner: anolisa-k8s-general-ci-x64-4vmvk-runner-gldw8
• Log shows:

  USE_VPC_MIRROR: true
  Trying VPC Alinux mirror (1/2)
  Importing Alinux GPG key from http://mirrors.cloud.aliyuncs.com/alinux/4/RPM-GPG-KEY-ALINUX-4
  

• No fallback log appeared:

  VPC Alinux mirror failed; falling back to public mirror
  

• Repo metadata download also completed via the selected mirror with normal speed:

  alinux4-os       331 MB/s | 11 MB | 00:00
  alinux4-updates   50 MB/s | 14 MB | 00:00
  

So ARC jobs are using the ECS/VPC mirror successfully, while GitHub-hosted manual runs still use the public mirror path.