NXP backend: handle tests of mlperf tiny classification

[novak-vaclav]

Summary

Enable and refactor MLPerf Tiny Classification tests.

Test plan

tests can be manually run using pytest -c /dev/null backends/nxp/tests/

cc @robert-kalmar @JakeStevens @digantdesai @rascani @roman-janik-nxp

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/21811

• 📄 Preview Python docs built from this PR

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❌ 1 New Failure

As of commit 5bc01b6 with merge base bf2103d ():

NEW FAILURE - The following job has failed:

• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 7ca4d73bd65d908d6ae0899ffcca3f3b63bcbbcbd26cea3653b363fde51cdbcd /exec failed with exit code 1

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[linux-foundation-easycla]

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