[Refactor]Refactor of vllm_ascend/distributed module (#5719)

### What this PR does / why we need it?
Based on the RFC:https://github.com/vllm-project/vllm-ascend/issues/5604

This PR is a refactoring of vllm_ascend/distributed, moving all
kv_transfer realtaed codes into a dedicated folder, which has already
been done in vLLM

### Does this PR introduce _any_ user-facing change?
NA

### How was this patch tested?


- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef

---------

Signed-off-by: lty <linhebiwen@gmail.com>

vllm_ascend/distributed/kv_transfer/utils/mooncake_transfer_engine.py

@@ -0,0 +1,53 @@
+import ipaddress
+import threading
+from typing import Optional
+
+from mooncake.engine import TransferEngine  # type: ignore
+
+
+class GlobalTE():
+
+    def __init__(self):
+        self.transfer_engine = None
+        self.is_register_buffer: bool = False
+        self.transfer_engine_lock = threading.Lock()
+        self.register_buffer_lock = threading.Lock()
+
+    def get_transfer_engine(self, hostname: str, device_name: Optional[str]):
+        try:
+            ip = ipaddress.ip_address(hostname)
+            if isinstance(ip, ipaddress.IPv6Address):
+                raise RuntimeError(
+                    "The backend of mooncake's Ascend Direct Xfer Library currently does not support IPv6."
+                )
+        except ValueError:
+            pass
+        if self.transfer_engine is None:
+            with self.transfer_engine_lock:
+                # Double-Checked Locking
+                if self.transfer_engine is None:
+                    if TransferEngine is None:
+                        raise RuntimeError("mooncake is not available")
+                    self.transfer_engine = TransferEngine()
+                    device_name = device_name if device_name is not None else ""
+                    ret_value = self.transfer_engine.initialize(
+                        hostname, "P2PHANDSHAKE", "ascend", device_name)
+                    if ret_value != 0:
+                        raise RuntimeError(
+                            f"TransferEngine initialization failed with ret_value: {ret_value}"
+                        )
+        return self.transfer_engine
+
+    def register_buffer(self, ptrs: list[int], sizes: list[int]):
+        with self.register_buffer_lock:
+            assert self.transfer_engine is not None, "Transfer engine must be initialized"
+            if self.is_register_buffer:
+                return
+            for ptr, size in zip(ptrs, sizes):
+                ret_value = self.transfer_engine.register_memory(ptr, size)
+                if ret_value != 0:
+                    raise RuntimeError("Mooncake memory registration failed.")
+            self.is_register_buffer = True
+
+
+global_te = GlobalTE()