Add LSTM unit test to arm backend

[SaoirseARM]

Summary

• Adding LSTM unit test for MI, BI, U55 and U85
• Includes just one sample input.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/7787

• 📄 Preview Python docs built from this PR

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❌ 2 New Failures, 3 Cancelled Jobs

As of commit 6cb41ed with merge base cd9ab87 ():

NEW FAILURES - The following jobs have failed:

• pull / test-phi-3-mini-runner-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 689d54baaac10fb2b245f5fd36c3d65aeee5bdec27ea7a9d94eb0f9caffabb7b /exec failed with exit code 2
• trunk / test-models-macos (cmake, emformer_transcribe, xnnpack-quantization-delegation, macos-m1-stable, 90) / macos-job (gh)
  RuntimeError: Missing out variants: {'quantized_decomposed::dequantize_per_tensor', 'quantized_decomposed::quantize_per_tensor'}

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

• trunk / test-models-macos (cmake, llama2, xnnpack-delegation, macos-m1-stable, 90) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-models-macos (cmake, mv3, portable, macos-m1-stable, 90) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-models-macos (cmake, vit, xnnpack-quantization-delegation, macos-m1-stable, 90) / macos-job (gh)
  ##[error]The operation was canceled.

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[SaoirseARM]

@pytorchbot label ciflow/trunk

[SaoirseARM]

@pytorchbot label "topic: not user facing"

[SaoirseARM]

@pytorchbot label 'partner: arm'

[digantdesai]

stamping to unblock merging.

[zingo]

Fails seems unrelated to PR and fails on other PR's also.