[1/N][CI] Add multi node test (#3359)

### What this PR does / why we need it?
This pr purpose to add multi-node test, on the first step, add
`deepseek-v3` dp+tp+ep test
### 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>

tests/e2e/multi_node/config/utils.py

@@ -0,0 +1,68 @@
+import os
+import socket
+import subprocess
+from typing import Optional, Tuple
+
+import psutil
+
+
+def get_leader_ip():
+    leader_dns = os.getenv("LWS_LEADER_ADDRESS")
+    assert leader_dns is not None, "cannot find leader address"
+    return socket.gethostbyname(leader_dns)
+
+
+def get_avaliable_port(start_port: int = 6000, end_port: int = 7000) -> int:
+    import socket
+    for port in range(start_port, end_port):
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+            try:
+                s.bind(("", port))
+                return port
+            except OSError:
+                continue
+    raise RuntimeError("No available port found")
+
+
+def get_net_interface(ip: Optional[str] = None) -> Optional[Tuple[str, str]]:
+    """
+    Returns specified IP and its network interface.
+    If no IP is provided, uses the first from hostname -I.
+    """
+    if ip is None:
+        ips = subprocess.check_output(["hostname",
+                                       "-I"]).decode().strip().split()
+        if not ips:
+            return None
+        ip = ips[0]
+
+    for iface, addrs in psutil.net_if_addrs().items():
+        for addr in addrs:
+            if addr.family == socket.AF_INET and addr.address == ip:
+                return ip, iface
+    return None
+
+
+def get_default_envs() -> dict[str, str]:
+    """Returns default network and system environment variables."""
+    result = get_net_interface()
+    if result is None:
+        raise RuntimeError("Failed to get default network IP and interface")
+    ip, nic_name = result
+
+    return {
+        "HCCL_IF_IP": ip,
+        "GLOO_SOCKET_IFNAME": nic_name,
+        "TP_SOCKET_IFNAME": nic_name,
+        "HCCL_SOCKET_IFNAME": nic_name,
+        "OMP_PROC_BIND": "false",
+        "OMP_NUM_THREADS": "100",
+        "VLLM_USE_V1": "1",
+        "HCCL_BUFFSIZE": "1024",
+        "VLLM_USE_MODELSCOPE": "true",
+        "NUMEXPR_MAX_THREADS": "100",
+    }
+
+
+def generate_ranktable():
+    pass