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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❌ 2 New Failures

As of commit 9358014 with merge base 2c706f1 ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 8545a2fb2a915fa542d260357a6d4423b80463ef0ca707504526ee36dc466305 /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-artifact / linux-job (gh)
  RuntimeError: Command docker exec -t 5092a2ef6fec838110e4e7ed268bd0f949131a6f262c94a5b8774a479cc51831 /exec failed with exit code 2

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[MartinPavella]

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