[feature] support pcp + mtp (in pd co-locate scenario) (#4098)

1. support pcp + mtp in pd co-locate scenario
2. llmdatadist connector pcp related bugfix and cleancode

- vLLM version: v0.11.0
- vLLM main:
83f478bb19

Signed-off-by: zhangsicheng5 <zhangsicheng5@huawei.com>

tests/ut/kv_connector/utils.py

@@ -164,7 +164,7 @@ def create_request(
                                   remote_host="my-host",
                                   remote_port=1234,
                                   remote_tp_size=1,
-                                  remote_cp_size=1,
+                                  remote_pcp_size=1,
                                   remote_dcp_size=1)
 
     max_tokens = 1 if do_remote_decode else max_tokens