Arm backend: Add arange.default dummy tests

[AdrianLundell]

Since we use unittests for coverage on the Edge IR op set which includes arange.default, we need tests for it even though it is decomposed to indicate that it has not been missed.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

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❌ 2 New Failures, 1 Pending, 1 Unrelated Failure

As of commit 5321dd2 with merge base b058afb ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
  >>> Lint for examples/models/llama/export_llama_lib.py:
• pull / android / build-llm-demo / linux-job (gh)
  RuntimeError: Command docker exec -t 8492f477916c98ae55049194564410305593f2fb4843e60082543063a96d01c3 /exec failed with exit code 2

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-llava-runner-linux / linux-job (gh) (trunk failure)
  test_llava_export

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[AdrianLundell]

Failures unrelated, this patch only introduces four new skipped tests, so very unlikely to cause any issues.