[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/kv_connector/test_mooncake_connector.py

@@ -1051,7 +1051,7 @@ class TestMooncakeConnectorWorker(unittest.TestCase):
                 'vllm_ascend.distributed.mooncake_connector.string_to_int64_hash',
                 mock_string_to_int64_hash),
             patch(
-                'vllm_ascend.distributed.mooncake.transfer_engine.TransferEngine',
+                'vllm_ascend.distributed.mooncake_transfer_engine.TransferEngine',
                 return_value=self.mock_transfer_engine),
             patch(
                 'vllm_ascend.distributed.mooncake_connector.KVCacheSendingThread',