KVCache Transfer via Layer-wise Strategy in Disaggregation (#2602)

### What this PR does / why we need it?
See RFC: https://github.com/vllm-project/vllm-ascend/issues/2470 This PR
add a new kv connector for layer-wised kv transfer

### Does this PR introduce _any_ user-facing change?
yes, a new kv connector is added. User can use layer wised feature now.
### How was this patch tested?


- vLLM version: v0.11.0rc3
- vLLM main:
https://github.com/vllm-project/vllm/commit/releases/v0.11.0

---------

Signed-off-by: leichao.lc <leichao139636@163.com>
Signed-off-by: CaveNightingale <2859066733@qq.com>
Signed-off-by: nwpu-zxr <zhouxuerong2@huawei.com>
Signed-off-by: wangxiaoteng <wangxiaoteng@huawei.com>
Signed-off-by: hanxinlong <50882499@qq.com>
Signed-off-by: liziyu <liziyu16@huawei.com>
Co-authored-by: CaveNightingale <2859066733@qq.com>
Co-authored-by: nwpu-zxr <zhouxuerong2@huawei.com>
Co-authored-by: wangxiaoteng <wangxiaoteng@huawei.com>
Co-authored-by: hanxinlong <50882499@qq.com>

examples/disaggregated_prefill_v1/load_balance_proxy_server_example.py

@@ -544,4 +544,4 @@ if __name__ == '__main__':
     global global_args
     global_args = parse_args()
     import uvicorn
-    uvicorn.run(app, host=global_args.host, port=global_args.port)
+    uvicorn.run(app, host=global_args.host, port=global_args.port)