Arm backend: Support per-channel in TOSA.RESCALE

[oscarandersson8218]

Adds support for per-channel rescaling in TOSA dialect RESCALE op.

cc @freddan80 @per @zingo @digantdesai

[pytorch-bot]

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❗ 1 Active SEVs

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• AWS was down, GHA infrastructure effected / recovering

❌ 7 New Failures, 1 Pending, 3 Unrelated Failures

As of commit 0f6325d with merge base 50e5ec0 ():

NEW FAILURES - The following jobs have failed:

• Build Presets / apple (ios) / build (gh)
  The process '/opt/homebrew/bin/git' failed with exit code 128
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t dece9880debcecee91c84d2adf906d366ac572c669be9899d3e50b6d5a7f616f /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 31ab27111431daf406740c70bd4cbc72a40682b1a96cd206283e047bccd6b234 /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t 144b849172f6967e91b07d2e33c94ce3a1d69c44171610c273f704bdc00f21e8 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 85cd95d068534c31fc0527203b1edec94f768ef856e9bfc251e22c5251243be3 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t 9998d33e41cbd378c8cec4c6cdb1240b26589fc60727d74eb0bc3e482a18981b /exec failed with exit code 2
• Test Metal Backend / export-voxtral-metal-artifact / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 2

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 / linux / linux-job (gh) (trunk failure)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
• trunk / unittest-release / linux / linux-job (gh) (trunk failure)

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