Arm backend: Upcast index argument to int64 for aten.index_copy ops

[YufengShi-dudu]

Change-Id: I01dbb2b69c5689dbc8b5b56534996eb7d74828ff

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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✅ You can merge normally! (6 Unrelated Failures)

As of commit d9d5fd8 with merge base bf79544 ():

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-binary-size-linux-gcc / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-openvino-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-setup-linux-gcc / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/ops/test_conv1d.py::TestConv1d::test_qs8_conv1d_batchnorm_seq
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/ops/test_conv1d.py::TestConv1d::test_qs8_conv1d_batchnorm_seq
• trunk / unittest-release / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/ops/test_conv1d.py::TestConv1d::test_qs8_conv1d_batchnorm_seq

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[ArmRyan]

Approved and reviewed internally

[zingo]

Fails are unrelated, only editing existing files so buck2 builds files should not need to be changed.