[CI] Refator multi-node CI (#3487)

### What this PR does / why we need it?
Refactor the multi-machine CI use case. The purpose of this PR is to
increase the ease of adding multi-machine CI use cases, allowing
developers to add multi-machine cluster model testing use cases
(including PD separation) by simply adding a new YAML configuration
file.
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: v0.11.0rc3
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0

---------

Signed-off-by: wangli <wangli858794774@gmail.com>

examples/disaggregated_prefill_v1/README.md

@@ -205,7 +205,7 @@ vllm serve /models/deepseek_r1_w8a8 \
 Run proxy server on the first node:
 ```shell
 cd /vllm-workspace/vllm-ascend/examples/disaggregated_prefill_v1
-python toy_proxy_server.py --host 172.19.32.175 --port 1025 --prefiller-hosts 172.19.241.49 --prefiller-port 20002 --decoder-hosts 172.19.123.51 --decoder-ports 20002
+python load_balance_proxy_server_example.py --host 172.19.32.175 --port 1025 --prefiller-hosts 172.19.241.49 --prefiller-port 20002 --decoder-hosts 172.19.123.51 --decoder-ports 20002
 ```
 
 Verification

examples/disaggregated_prefill_v1/gen_ranktable.py

@@ -21,6 +21,10 @@ parser.add_argument("--local-device-ids",
                     type=str,
                     required=False,
                     help="local device ids")
+parser.add_argument("--ranktable-path",
+                    type=str,
+                    default="./ranktable.json",
+                    help="output rank table path")
 args = parser.parse_args()
 local_host = args.local_host
 prefill_device_cnt = args.prefill_device_cnt
@@ -130,7 +134,8 @@ ranktable = {
 }
 
 if local_rank == '0':
-    with open("ranktable.json", "w") as f:
+    os.makedirs(os.path.dirname(args.ranktable_path), exist_ok=True)
+    with open(args.ranktable_path, "w") as f:
         json.dump(ranktable, f, indent=4)
 
     print("gen ranktable.json done")