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>

tests/ut/distributed/test_parallel_state.py

@@ -4,8 +4,9 @@ import pytest
 from vllm.config import ParallelConfig
 
 from vllm_ascend.distributed.parallel_state import (
-    _LMTP, _MC2, _OTP, destroy_ascend_model_parallel, get_lmhead_tp_group,
-    get_mc2_group, get_otp_group, init_ascend_model_parallel)
+    _LMTP, _MC2, _OTP, _P_TP, destroy_ascend_model_parallel,
+    get_lmhead_tp_group, get_mc2_group, get_otp_group, get_p_tp_group,
+    init_ascend_model_parallel)
 
 
 @pytest.fixture
@@ -30,6 +31,7 @@ def test_init_ascend_model_parallel(mock_distributed, parallel_config):
     mock_ascend_config = MagicMock()
     mock_ascend_config.lmhead_tensor_parallel_size = 2
     mock_ascend_config.oproj_tensor_parallel_size = 2
+    mock_ascend_config.pd_tp_ratio = 2
     with patch('vllm_ascend.distributed.parallel_state.model_parallel_initialized', return_value=False), \
          patch('vllm_ascend.distributed.parallel_state.init_model_parallel_group'), \
          patch('vllm_ascend.distributed.parallel_state.get_ascend_config', return_value=mock_ascend_config):
@@ -38,11 +40,14 @@ def test_init_ascend_model_parallel(mock_distributed, parallel_config):
         mc2_group = get_mc2_group()
         lmheadtp_group = get_lmhead_tp_group()
         otp_group = get_otp_group()
+        p_tp_group = get_p_tp_group()
         assert mc2_group is not None
         assert otp_group is not None
         assert lmheadtp_group is not None
+        assert p_tp_group is not None
 
         destroy_ascend_model_parallel()
         assert _MC2 is None
         assert _LMTP is None
         assert _OTP is None
+        assert _P_TP is None