[Fix] Adds CUDA graph stats to execution state (#6331)

### What this PR does / why we need it?
Adds a CUDA graph profiling stats field to the execution state and
updates the NPU model runner to set, unpack, and forward those stats
during execution. This preserves CUDA graph metrics across state
transitions, improving observability for later use and diagnostics.

### Does this PR introduce _any_ user-facing change?
Enable this by set
```python
    llm = LLM(
        ...
        disable_log_stats=False,
        cudagraph_metrics=True,
        ...
    )
```
or `--cudagraph-metrics` and make sure do not disable log stats.

After this, you should be able to see something like this, which is
really helpful for some light debugging:
```
[loggers.py:257] Engine 000: Avg prompt throughput: 32.3 tokens/s, Avg generation throughput: 114.4 tokens/s, Running: 4 reqs, Waiting: 0 reqs, GPU KV cache usage: 0.1%, Prefix cache hit rate: 0.0%
[cuda_graph.py:117] **CUDAGraph Config Settings:**
[cuda_graph.py:117] 
[cuda_graph.py:117] - Mode: FULL_DECODE_ONLY
[cuda_graph.py:117] - Capture sizes: [1, 2, 4, 8, 16, 24, 32]
[cuda_graph.py:117] 
[cuda_graph.py:117] **CUDAGraph Stats:**
[cuda_graph.py:117] 
[cuda_graph.py:117] | Unpadded Tokens | Padded Tokens | Num Paddings | Runtime Mode | Count |
[cuda_graph.py:117] |-----------------|---------------|--------------|--------------|-------|
[cuda_graph.py:117] | 4               | 4             | 0            | FULL         | 18    |
[cuda_graph.py:117] | 5               | 5             | 0            | NONE         | 1     |
[cuda_graph.py:117] | 1               | 1             | 0            | FULL         | 1     |
[cuda_graph.py:117] | 18              | 18            | 0            | NONE         | 1     |
```

### How was this patch tested?
None.

- vLLM version: v0.14.1
- vLLM main:
dc917cceb8

Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>

vllm_ascend/worker/model_runner_v1.py

@@ -192,6 +192,7 @@ class ExecuteModelState(NamedTuple):
     attn_metadata: "PerLayerAttnMetadata"
     positions: torch.Tensor
     ec_connector_output: "ECConnectorOutput | None"
+    cudagraph_stats: CUDAGraphStat | None
 
 
 class NPUModelRunner(GPUModelRunner):
@@ -1353,6 +1354,7 @@ class NPUModelRunner(GPUModelRunner):
                 attn_metadata,
                 positions,
                 ec_connector_output,
+                cudagraph_stats,
             )
             self.kv_connector_output = kv_connector_output
         return None
@@ -1389,6 +1391,7 @@ class NPUModelRunner(GPUModelRunner):
             attn_metadata,
             positions,
             ec_connector_output,
+            cudagraph_stats,
         ) = self.execute_model_state
         # Clear ephemeral state.
         self.execute_model_state = None
@@ -1466,6 +1469,7 @@ class NPUModelRunner(GPUModelRunner):
             ec_connector_output=ec_connector_output
             if self.supports_mm_inputs
             else None,
+            cudagraph_stats=cudagraph_stats,
         )
 
         durations = ProfileExecuteDuration().pop_captured_sync()