[E2E] Optimize the E2E test time. (#5294)

### What this PR does / why we need it?
Add cudagraph_capture_sizes for E2E CI test.

- vLLM version: release/v0.13.0
- vLLM main:
ad32e3e19c

Signed-off-by: menogrey <1299267905@qq.com>

tests/e2e/singlecard/test_sampler.py

@@ -32,6 +32,7 @@ def test_qwen3_topk() -> None:
 
     with VllmRunner("Qwen/Qwen3-0.6B",
                     max_model_len=8192,
+                    cudagraph_capture_sizes=[1, 2, 4, 8],
                     gpu_memory_utilization=0.7) as runner:
         runner.generate(example_prompts, sampling_params)
 
@@ -43,6 +44,7 @@ def test_qwen3_prompt_logprobs() -> None:
 
     with VllmRunner("Qwen/Qwen3-0.6B",
                     max_model_len=8192,
+                    cudagraph_capture_sizes=[1, 2, 4, 8],
                     gpu_memory_utilization=0.7) as runner:
         runner.generate_greedy_logprobs(example_prompts,
                                         max_tokens=5,
@@ -60,6 +62,7 @@ def test_qwen3_exponential_overlap() -> None:
 
     with VllmRunner("Qwen/Qwen3-0.6B",
                     max_model_len=8192,
+                    cudagraph_capture_sizes=[1, 2, 4, 8],
                     gpu_memory_utilization=0.7,
                     additional_config={
                         "enable_async_exponential": True,