Arm backend: Fix deepcopy & require grad issues.

[Michiel-Olieslagers]

Change-Id: I7a813807c0e7a2734a96c317d2f198ae489de285

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani

[pytorch-bot]

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❌ You can merge normally! (1 Unrelated Failure), 1 Unclassified Failure

As of commit e7f45c9 with merge base c4e3db0 ():

UNCLASSIFIED FAILURE - DrCI could not classify the following job because the workflow did not run on the merge base. The failure may be pre-existing on trunk or introduced by this PR:

• trunk / test-models-macos-cpu (ic4, xnnpack-quantization-delegation) / macos-job (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.arm64.2xlarge, executorch-ubuntu-22.04-gc... / linux-job (gh) (matched linux rule in flaky-rules.json)
  docker: Error response from daemon: Head "https://registry-1.docker.io/v2/arm64v8/alpine/manifests/latest": Get "https://auth.docker.io/token?account=pytorchbot&scope=repository%3Aarm64v8%2Falpine%3Apull&service=registry.docker.io": context deadline exceeded (Client.Timeout exceeded while awaiting headers).

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