NXP backend: Update cat delegation.

[MartinPavella]

Summary

This PR updates the aten.cat.default delegation condition to more accurately match the requirements of Neutron.

Test plan

Unit tests provided.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/14580

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❌ 3 New Failures, 1 Unrelated Failure

As of commit 4067d90 with merge base 70ea661 ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 3f48f29818fc4ebe224683230e0efa18b4586b1c29d194147e45df9a416565c2 /exec failed with exit code 1
• pull / test-vulkan-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t f36b0adf6882b43af82124167337750bf172a17c786573bd7d661c14a0a937f3 /exec failed with exit code 1
• Test CUDA Builds / test-voxtral-cuda-e2e / linux-job (gh)
  RuntimeError: Command docker exec -t 02a2aeeacf1bdac73ab47ed6513a4fbf493d5a51b2bba52a78f1825eb6e81f7c /exec failed with exit code 2

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

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

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[MartinPavella]

Only the last commit is relevant. Once another PR is merged, the commit will be re-based.