Arm backend: Various fixes to get per channel quantization in place

[per]

Summary

First series of patches to enable per channel quantization

Test plan

Arm backend unit tests

cc @digantdesai @freddan80 @zingo @oscarandersson8218

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/9487

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❌ 4 New Failures

As of commit 4a452b5 with merge base a6cd1dc ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
  >>> Lint for examples/qualcomm/utils.py:
• pull / test-eval_llama-mmlu-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 7f57a2a58e9b986f1d57bc3f4b0d68747c0eebed78aac884f4211be0661b676e /exec failed with exit code 1
• trunk / test-qnn-model (fp32, mb) / linux-job (gh)
  RuntimeError: Command docker exec -t c2cc389f1eded15e8944955d9628cfafa0e045ff69aadc84c0316753f783e191 /exec failed with exit code 1
• trunk / unittest-release / macos / macos-job (gh)
  backends/xnnpack/test/passes/test_convert_to_linear.py::TestConvertToLinear::test_fp32_convert_to_linear

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[per]

Unrelated failures.

[zingo]

Fails seem unrelated