[Feature][main]reconstruction kvpool connector to ascend connector (#4438)

### What this PR does / why we need it?
1.In short, we renamed the existing MooncakeStoreConnector to
AscendStoreConnector and extracted the storage engine interaction logic
into a new Backend class.
Associated RFC：https://github.com/vllm-project/vllm-ascend/issues/4329
2.Fixed the issue where the number of input parameters for the connector
was incorrect, introduced in vllm 0.11.2
### Does this PR introduce _any_ user-facing change?
change MooncakeStoreConnector to AscendStoreConnector
### How was this patch tested?

- vLLM version: v0.11.2

---------

Signed-off-by: fems14 <1804143737@qq.com>

tests/ut/distributed/mooncake/test_config_data.py

@@ -1,6 +1,13 @@
+import sys
+import types
 import unittest
+from unittest.mock import MagicMock
 
-from vllm_ascend.distributed.mooncake.config_data import (
+fake_engine = types.ModuleType("mooncake.engine")
+fake_engine.TransferEngine = MagicMock()  # type: ignore[attr-defined]
+sys.modules["mooncake.engine"] = fake_engine
+
+from vllm_ascend.distributed.kvpool.backend.mooncake_backend import (  # noqa: E402
     _convert_to_bytes, _parse_global_segment_size)