Arm backend: Add TOSA binary op visitors

[SaoirseARM]

Summary

• Running the cast pass first normalizes constant buffers while the graph is still Edge ATen, so ExirToTosaPass only sees int32 buffer metadata and emits TOSA-compatible ops.
• Small refactor of ExirToTosaPass

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

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/20479

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• [ROCm] MI350 CI jobs will have longer queue times due to CI migration

❌ 5 New Failures, 5 Unrelated Failures

As of commit b8522b0 with merge base 252f57c ():

NEW FAILURES - The following jobs have failed:

• pull / test-arm-backend-no-driver (test_pytest_models_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 1108e044b2d8b8f5fdedece14834561d3c06286fe1de1ea21e27c3a696c6a7ea /exec failed with exit code 1
• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t 9eacf036b872b783f84c492ec0cd080fb1564fc468a022bec741635e792e003c /exec failed with exit code 139
• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 378d1c989515f7285eeb4f8d0a5fe0358ea01c6468dd5a8e608893d32c7b59c5 /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 23a74fa2ca46ceb1f24cab8b76c4e9de98066b4a13fdfa9daafe88538833b2bf /exec failed with exit code 1
• trunk / unittest-release / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 128a4613fcd05726ce65c220ffbc00c6a45f6aeacefad00143e08db9ba31346b /exec 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 / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh) (trunk failure)
• pull / unittest / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• trunk / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh) (trunk failure)
• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[SaoirseARM]

@pytorchbot label ciflow/trunk

[SaoirseARM]

@pytorchbot label 'partner: arm'

[SaoirseARM]

@pytorchbot label "release notes: arm"

[zingo]

OK to merge if tests are OK, just make sure buck2 stuff don't need to be updated. You can just ask codex/claude

[zingo]

FAILED backends/arm/test/misc/test_vgf_backend.py::test_vgf_compile_failure_includes_repro_command_and_copies_tosa

Is known and a fix has been merged, just rebase or double check to there are no others files.