Arm backend: Improve support for multiple output ops

[Erik-Lundell]

The pattern of using .name from the TosaArg output is used in essentially all node visitors. Refactoring output to possibly be a list of TosaArgs would be very cumbersome. Instead, use a new multiple_output_names field to provide the names of all getitem tensors. This also means that we don't have to insert identity ops for getitem operators, they just need to insert a tensor.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 3 New Failures, 6 Unrelated Failures

As of commit 7e2e5ed with merge base c8e9684 ():

NEW FAILURES - The following jobs have failed:

• Test CUDA Builds / check-all-cuda-builds (gh)
  Process completed with exit code 1.
• Test CUDA Builds / test-executorch-cuda-build-12.8 / linux-job (gh)
  RuntimeError: Command docker exec -t 19fb72ccb514bde31cc5d8a7fa440f8daae5931e81723bf88f59168b897bc499 /exec failed with exit code 1
• trunk / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh)
  RuntimeError: Command docker exec -t adaa1219464d6e54dcbccabf7bd689e6f0ccf8ca03dee9fab3bdedce5fe782d6 /exec failed with exit code 92

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)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• pull / unittest / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• trunk / unittest-release / linux / linux-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe

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[Erik-Lundell]

Unrelated failure, should be buck safe

[zingo]

fails are unrelated