Arm backend: Move rescales from ADD & SUB visitors to pass

[martinlsm]

Move the insertion of INT8/INT32 RESCALE ops from the SUB node visitor to the pass InsertRescaleInt32Pass.

This is in practice a refactoring patch, but still the output TOSA files becomes different enough to cause Ethos-U55/U85 tests to fail in test_var.py and test_conv_relu_residual_add.py. However, the issue was fixed in https://gitlab.arm.com/artificial-intelligence/ethos-u/ethos-u-vela/-/commit/642f7517d3a6bd053032e1942822f6e38ccd546f so we temporarily set the failing tests to xfail until the version of Ethos-U Vela compiler depended on is bumped to one that includes the fix.

Test plan

test_insert_rescale_i32_pass.py has been modified to test the change.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 8 New Failures, 1 Cancelled Job, 3 Unrelated Failures

As of commit 07d8738 with merge base de56c81 ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t b25e84740c771b1550548340e7f73570e0b8dcdf79912d9dc059db38539c03df /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 2158e1d688549373a186558352d227c1ff6dd2b1d4d76f5d0f7abb053f07f2b7 /exec failed with exit code 1
• Test CUDA Builds / export-gemma3-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t a262a9346855ee5e557dc3cc1a785f194384c2421fbfc2bf307fe82282383387 /exec failed with exit code 2
• Test CUDA Builds / export-gemma3-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 320c96f6a690995c80018937df7a2b8df55561aeb8522df038bc1a47c3aad72b /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t 020241618b524f563b3297d75ed01733af18e8a0869d5903abc520f56ea4d1dd /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 3a7b7b430b464119175800127d8a46f02e3da7d750e69f1336298c98afc4a29e /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t f971ccd4fb43b57f3cd6be0b658f0f4df8ec2cb0cc405883bab7ddacb6bff09c /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

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / unittest-editable / macos / macos-job (gh)
  ##[error]The operation was canceled.

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following jobs failed but was present on the merge base:

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

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

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[martinlsm]

@pytorchbot label ciflow/trunk

[martinlsm]

@pytorchbot label "partner: arm"

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