Arm Backend: Add support for split_copy.default

[agrima1304]

Add support for partly supported split_copy operator that was already decomposed into multiple slice operators, but was not fully supported in the Arm backend.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

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❌ 5 New Failures, 5 Unrelated Failures

As of commit 78181c4 with merge base d00279d ():

NEW FAILURES - The following jobs have failed:

• pull / test-qnn-wheel-packages-linux (3.10) / linux-job (gh)
  RuntimeError: Command docker exec -t 1824349e6fa70bd4a0b81aa470a93d662f8fe40e3e84bc21d0f8cb95da5da47a /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.11) / linux-job (gh)
  RuntimeError: Command docker exec -t bb44a0dc5ac5a7127d8d71a7b0c7ddafe6b85e5ff10f49c8e641f73f7d4df669 /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.12) / linux-job (gh)
  RuntimeError: Command docker exec -t b1fbf78cc0cb650c159f31bde3962c2d9cdc152146da72c79e0ebda8c8a276a0 /exec failed with exit code 1
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 89e4fe2afc27d33629e7760b5f9fab1e001283af62b9186c4dfc4292ec9163f8 /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-artifact / linux-job (gh)
  RuntimeError: Command docker exec -t ecf628a3175053da3cf7590fc3dcfb3f48a437c05190154dba321fadadbb2d7c /exec failed with exit code 2

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.
• pull / unittest-editable / linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.
• pull / unittest-editable / macos / macos-job (gh) (similar failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script 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)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-buck / 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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[agrima1304]

@pytorchbot label "partner: arm"

[agrima1304]

@pytorchbot label "release notes: arm"

[agrima1304]

@pytorchbot label "ciflow/trunk"

[pytorch-bot]

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