[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>

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

@@ -44,7 +44,6 @@ deployment:
         "kv_role": "kv_producer",
         "kv_port": "30000",
         "engine_id": "0",
-        "kv_connector_module_path": "vllm_ascend.distributed.mooncake_connector",
         "kv_connector_extra_config": {
                   "use_ascend_direct": true,
                   "prefill": {
@@ -84,7 +83,6 @@ deployment:
         "kv_role": "kv_consumer",
         "kv_port": "30100",
         "engine_id": "1",
-        "kv_connector_module_path": "vllm_ascend.distributed.mooncake_connector",
         "kv_connector_extra_config": {
                   "use_ascend_direct": true,
                   "prefill": {