Add sum.dim_IntList to RemovePermutesAroundElementwiseOps

[mcremon-meta]

Summary:
DecomposeMeanDimPass decomposes mean.dim into sum.dim_IntList + mul.Tensor.
While mean.dim and mul.Tensor are both in the permutable_ops set of
RemovePermutesAroundElementwiseOps, sum.dim_IntList is not — so the pass
cannot traverse through the decomposed chain to find the matching exit permute.

This adds aten.sum.dim_IntList to permutable_ops with the same keepdim
validation and dimension-adjustment logic already used for mean.dim. This is
safe because:

• sum.dim_IntList has identical dimension semantics to mean.dim
• DecomposeMeanDimPass always calls sum with keepdim=True
• mul.Tensor (the other half of the decomposition) is already handled

Reviewed By: 3l1

Differential Revision: D103272273

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell

[pytorch-bot]

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❌ 3 New Failures, 2 Unrelated Failures

As of commit a4593f1 with merge base 94d2881 ():

NEW FAILURES - The following jobs have failed:

• pull / test-coreml-bc-macos (macos-m1-stable) / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• trunk / test-selective-build-macos (cmake) / macos-job (gh)
  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-editable / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[meta-codesync]

@mcremon-meta has exported this pull request. If you are a Meta employee, you can view the originating Diff in D103272273.

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[gggekov]

Looks good.