Add Qwen 3.5 MoE to cuda-perf CI and add prefill throughput tracking

[Gasoonjia]

• Add PyTorchObserver stats output to qwen3_5_moe runner (enables cuda_benchmark.py parsing), --prompt_file flag, and GPU memory stats
• Add prefill_throughput metric to cuda_benchmark.py (prefill tok/s alongside existing decode tok/s)
• Add Qwen3.5-35B-A3B-HQQ-INT4 to cuda-perf.yml with >1000 token prompt and 512 output tokens, on linux.aws.a100
• Align cuda-perf.yml triggers with cuda.yml (push main/release, ciflow/cuda tags, PR on backends/cuda and backends/aoti paths)
• Remove random model selection and schedule trigger; always run all models when triggered

[pytorch-bot]

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❗ 1 Active SEVs

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• [CI[B200] Smoke test encounters CUDA Unknown error for dgxb200-03 and dgxb200-04

❌ 7 New Failures, 4 Cancelled Jobs, 1 Unrelated Failure

As of commit 7336416 with merge base 28c56fe ():

NEW FAILURES - The following jobs have failed:

• pull / android / run-emulator (gh)
  The process '/usr/local/lib/android/sdk/platform-tools/adb' failed with exit code 224
• pull / unittest / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_mv3_model
• pull / unittest-arm-backend-with-no-deps (test_pytest_ops_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 6a9ea35c4e2844833c6eb803902fdf811c823d21b39f5e5fa230ecbb7a8b136e /exec failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_mv3_model
• trunk / test-torchao-huggingface-checkpoints (lfm2_5_1_2b, linux.arm64.2xlarge, executorch-ubuntu-22.04-g... / linux-job (gh)
  RuntimeError: Command docker exec -t 13ba2a762a54b4ab0b39bc45b1d34ef72d70a86eae2221ebc18c40d409573f97 /exec failed with exit code 1
• trunk / test-torchao-huggingface-checkpoints (phi_4_mini, linux.arm64.2xlarge, executorch-ubuntu-22.04-gc... / linux-job (gh)
  RuntimeError: Command docker exec -t 95b0017e20b9e4ecc6ce1faa320d2d03c396f8c4fb553657fab4f574f3df43fb /exec failed with exit code 1
• trunk / test-torchao-huggingface-checkpoints (qwen3_4b, linux.arm64.2xlarge, executorch-ubuntu-22.04-gcc1... / linux-job (gh)
  RuntimeError: Command docker exec -t b02f1d8a2b04d3331eb654ef2bc0318964344cfeb83c22c0219816b090c02b92 /exec failed with exit code 1

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• pull / unittest / windows / windows-job (gh)
• trunk / test-llama-runner-mac (fp32, coreml) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-models-macos-coreml (edsr) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / unittest-release / windows / windows-job (gh)

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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