[Refactor] [SP]The sequence parallelism characteristics in the MoE and Dense models are integrated into a single solution. (#3085)

What this PR does / why we need it?

there are two sets of sp implementations for moe and dense models. One
is called sequence_parallelism, and the other is flashcomm_v1.
We did the following things：

Merge two sets of code with the same implementation into one.
Remove the implementation of sequence_parallelism, as this solution
cannot support aclgraph.
Does this PR introduce any user-facing change?

No

How was this patch tested?

e2e&ut

- vLLM version: v0.10.2
- vLLM main:
f225ea7dd9

---------

Signed-off-by: weijinqian_v1 <weijinqian@huawei.com>
Co-authored-by: weijinqian_v1 <weijinqian@huawei.com>

vllm_ascend/worker/model_runner_v1.py

@@ -1582,7 +1582,7 @@ class NPUModelRunner(LoRAModelRunnerMixin):
             update_attn_params(self.update_stream, forward_context,
                                positions.shape[0])
 
-        if get_forward_context().flashcomm_v1_enabled:
+        if get_forward_context().sp_enabled:
             hidden_states = tensor_model_parallel_all_gather(hidden_states, 0)
             pad_size = get_forward_context().pad_size
             if pad_size > 0: