[1/N] Refactor nightly test structure (#5479)

### What this PR does / why we need it?
This patch is a series of refactoring actions, including clarifying the
directory structure of nightly tests, refactoring the config retrieval
logic, and optimizing the workflow, etc. This is the first step:
refactoring the directory structure of nightly to make it more readable
and logical.

- vLLM version: v0.13.0
- vLLM main:
5326c89803

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

tests/e2e/nightly/multi_node/config/Qwen3-235B-A22B.yaml

@@ -0,0 +1,70 @@
+test_name: "test Qwen3-235B-A22B multi-dp"
+model: "Qwen/Qwen3-235B-A22B"
+num_nodes: 2
+npu_per_node: 16
+env_common:
+  VLLM_USE_MODELSCOPE: true
+  OMP_PROC_BIND: false
+  OMP_NUM_THREADS: 100
+  HCCL_BUFFSIZE: 1024
+  SERVER_PORT: 8080
+  NUMEXPR_MAX_THREADS: 128
+
+deployment:
+  -
+    server_cmd: >
+        vllm serve "Qwen/Qwen3-235B-A22B"
+        --host 0.0.0.0
+        --port $SERVER_PORT
+        --data-parallel-size 4
+        --data-parallel-size-local 2
+        --data-parallel-address $LOCAL_IP
+        --data-parallel-rpc-port 13389
+        --tensor-parallel-size 8
+        --seed 1024
+        --enable-expert-parallel
+        --max-num-seqs 32
+        --max-model-len 8192
+        --max-num-batched-tokens 8192
+        --trust-remote-code
+        --no-enable-prefix-caching
+        --gpu-memory-utilization 0.9
+  -
+    server_cmd: >
+        vllm serve "Qwen/Qwen3-235B-A22B"
+        --headless
+        --data-parallel-size 4
+        --data-parallel-size-local 2
+        --data-parallel-start-rank 2
+        --data-parallel-address $MASTER_IP
+        --data-parallel-rpc-port 13389
+        --tensor-parallel-size 8
+        --seed 1024
+        --max-num-seqs 32
+        --max-model-len 8192
+        --max-num-batched-tokens 8192
+        --enable-expert-parallel
+        --trust-remote-code
+        --no-enable-prefix-caching
+        --gpu-memory-utilization 0.9
+benchmarks:
+  perf:
+    case_type: performance
+    dataset_path: vllm-ascend/GSM8K-in3500-bs2800
+    request_conf: vllm_api_stream_chat
+    dataset_conf: gsm8k/gsm8k_gen_0_shot_cot_str_perf
+    num_prompts: 2800
+    max_out_len: 1500
+    batch_size: 700
+    request_rate: 11.2
+    baseline: 1
+    threshold: 0.97
+  acc:
+    case_type: accuracy
+    dataset_path: vllm-ascend/gsm8k
+    request_conf: vllm_api_general_chat
+    dataset_conf: gsm8k/gsm8k_gen_0_shot_cot_chat_prompt
+    max_out_len: 7680
+    batch_size: 512
+    baseline: 95
+    threshold: 3