support cp&dcp (#3260)

### What this PR does / why we need it?
This PR adds the Prefill Context Parallelism (PCP) feature, which
corresponds to DCP. For specific implementation details, please refer to
the RFC https://github.com/vllm-project/vllm/issues/25749.
TL;DR: PCP enhances long-sequence inference capabilities by partitioning
the sequence dimension during the prefill stage.
### Does this PR introduce _any_ user-facing change?
The current implementation primarily includes the following changes:

Modified ModelRunner.py for CP partitioning logic for tokens;
Modified attention_v1.py and mla_v1.py to adapt the GQA/MLA backend to
PCP.
Modified block_tables.py to extend the KV cache storage based on
DCP&PCP;
Added necessary command-line arguments to control parallelism for PCP;
### How was this patch tested?


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

---------

Signed-off-by: LookAround <lixushi@huawei.com>
Signed-off-by: chenjie <chenjie137@huawei.com>
Signed-off-by: Delphine-Nic <tanwenqin@huawei.com>
Signed-off-by: zhangsicheng5 <zhangsicheng5@huawei.com>
Signed-off-by: Feng Liu <liufeng248@huawei.com>
Signed-off-by: gaojc <1055866782@qq.com>
Signed-off-by: weiguihua2 <weiguihua2@huawei.com>
Signed-off-by: z50049692 <zhangmingwei11@huawei.com>
Co-authored-by: chenjie <chenjie137@huawei.com>
Co-authored-by: Delphine-Nic <tanwenqin@huawei.com>
Co-authored-by: zhangsicheng5 <zhangsicheng5@huawei.com>
Co-authored-by: Feng Liu <liufeng248@huawei.com>
Co-authored-by: gaojc <1055866782@qq.com>
Co-authored-by: weiguihua2 <weiguihua2@huawei.com>
Co-authored-by: z50049692 <zhangmingwei11@huawei.com>
Co-authored-by: w00896881 <wangzixuan40@huawei.com>

vllm_ascend/worker/worker_v1.py

@@ -49,6 +49,7 @@ from vllm_ascend.device_allocator.camem import CaMemAllocator
 from vllm_ascend.distributed.parallel_state import init_ascend_model_parallel
 from vllm_ascend.platform import NPUPlatform
 from vllm_ascend.utils import (init_ascend_soc_version,
+                               prefill_context_parallel_enable,
                                register_ascend_customop, sleep_mode_enabled,
                                try_register_lib)
 from vllm_ascend.worker.model_runner_v1 import NPUModelRunner
@@ -381,9 +382,17 @@ class NPUWorker(WorkerBase):
         init_distributed_environment(self.parallel_config.world_size,
                                      self.rank, self.distributed_init_method,
                                      self.local_rank, "hccl")
-        ensure_model_parallel_initialized(
-            self.parallel_config.tensor_parallel_size,
-            self.parallel_config.pipeline_parallel_size)
+        if prefill_context_parallel_enable():
+            ensure_model_parallel_initialized(
+                self.parallel_config.tensor_parallel_size,
+                self.parallel_config.pipeline_parallel_size,
+                self.parallel_config.prefill_context_parallel_size,
+                self.parallel_config.decode_context_parallel_size)
+        else:
+            ensure_model_parallel_initialized(
+                self.parallel_config.tensor_parallel_size,
+                self.parallel_config.pipeline_parallel_size,
+                self.parallel_config.decode_context_parallel_size)
         init_ascend_model_parallel(self.parallel_config)
         ensure_kv_transfer_initialized(self.vllm_config)