Arm backend: Fuse duplicate user ops

[AdrianLundell]

Adds a pass which checks if a node has multiple users performing equivalent operations its output. If that is the case, it fuses these ops into one.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15218

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• AWS was down, GHA infrastructure effected / recovering

❌ 8 New Failures, 1 Cancelled Job, 5 Unrelated Failures

As of commit f3bd07c with merge base 73f7286 ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 7b14cf450fffe41c469d9b67c09ef9b20325a351f88bed5885912e188cbbbf31 /exec failed with exit code 1
• pull / unittest-arm-backend-with-no-fvp (test_pytest_models) / linux-job (gh)
  RuntimeError: Command docker exec -t 6d13faeade35a228ff6700d0089b4441bf41d7038a8227a50904a4f813c37ea0 /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t f315277b404724da46a8c5a2ac5900d82984074d08bf62a0d96a01737d176825 /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t 4188be3b411cb3a805ea08e47476bf737536bbc749af9fefd7105953adb1c3f0 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t d5c8bb75387b8e50e095a6fde4ed40c1ee9f125cabf84f7810d158b2389a5b15 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t 5230d050bba8b404f48d4e3978e5b0fe776183d1fccc440c8aa94831b3da8a04 /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
• trunk / test-arm-backend (test_pytest_models_ethosu_fvp) / linux-job (gh)
  RuntimeError: Command docker exec -t 9de1c449187cb95e44668e74747dc735812cf359509be393b36b328dbbae9c10 /exec failed with exit code 1

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

• trunk / test-models-macos-cpu (mv3, xnnpack-quantization-delegation) / macos-job (gh)
  ##[error]The operation was canceled.

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

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

• Build documentation / build (buck2) / Build doc (gh) (trunk failure)
• pull / android / run-emulator (gh) (trunk failure)
  The process '/usr/bin/sh' failed with exit code 255
• 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)

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