[ExecuTorch][WebGPU] et_vk.embedding_q4gsw test suite (export + native golden)

[pytorchbot]

This PR was created by the merge bot to help merge the original PR into the main branch.
ghstack PR number: #20289 by @JulianCloudNTH
^ Please use this as the source of truth for the PR details, comments, and reviews
ghstack PR base: https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/28/base
ghstack PR head: https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/28/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/25/orig
Merge bot PR head: https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/28/orig

@diff-train-skip-merge

[pytorch-bot]

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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/20416

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❗ 1 Active SEVs

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• [ROCm] MI350 CI jobs will have longer queue times due to CI migration

❌ 5 New Failures, 2 Unrelated Failures

As of commit 58786be with merge base 0e65ba6 ():

NEW FAILURES - The following jobs have failed:

• pull / test-lora-multimethod-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 12dc7fe966ebaa3096b1597c0c070ba6645526654b27b30b65d6a7281b303e1c /exec failed with exit code 1
• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t 4b293ed9c89a744e541bdb7d8e224f7feeb7936dd4dd4f045c7ec6feb0f66398 /exec failed with exit code 139
• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 2b04abef7fcad6676146e2e47ba71df3714752362089b895024a429403289ee3 /exec failed with exit code 1
• pull / unittest / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 345f60d69f32596d9e1aa3205d124ab4a8de303f8d237b83767a3a8e79fac19d /exec 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 / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh) (trunk failure)
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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