[CI] Switching to infra cache server to reduce network pressure (#1792)

### What this PR does / why we need it?
This PR introduce the infra cache server to speed up apt/pip package
installation

### Does this PR introduce _any_ user-facing change?
None

### How was this patch tested?
Tested locally, with this config, the network bandwith reduce from 100%
to 5% usage when a new PR was submitted.
<img width="807" height="334" alt="image"
src="https://github.com/user-attachments/assets/16f03bce-4531-4c71-ab6e-8308dc2c022c"
/>


- vLLM version: v0.9.2
- vLLM main:
8dfb45ca33

---------

Signed-off-by: mywaaagh_admin <pkwarcraft@gmail.com>

.github/workflows/vllm_ascend_test_pd.yaml

@@ -73,6 +73,7 @@ jobs:
 
       - name: Config mirrors
         run: |
+          # keep using tuna's proxy since linux-arm64-npu-static-8 is in another region
           sed -i 's|ports.ubuntu.com|mirrors.tuna.tsinghua.edu.cn|g' /etc/apt/sources.list
           pip config set global.index-url https://mirrors.tuna.tsinghua.edu.cn/pypi/web/simple
           apt-get update -y