Draft: New Neutron-C flow support for ReLU

[StrycekSimon]

Summary

Removes unnecessary checks for ReLU conversion when using new Neutron-C flow.

Test plan

New unit test cases were added.

cc @digantdesai @robert-kalmar @JakeStevens

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19275

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❗ 1 Active SEVs

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❌ 2 New Failures, 3 Unrelated Failures

As of commit 30cd6a6 with merge base a6ee309 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 739a2d1f26992a84e90c5650986f723b8d75624bcaad84a99a0fc3f46716300a /exec failed with exit code 1
• trunk / test-huggingface-transformers-macos (smollm2-135m|coreml_fp32_gpu|--quantize) / macos-job (gh)
  The process '/opt/homebrew/bin/git' failed with exit code 1

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

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

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

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[pytorch-bot]

Workflows were awaiting approval. CI has now been triggered for the ciflow labels on this PR.