NXP backend: Add tanh support with new Neutron flow.

[MartinPavella]

Summary

Add tanh support with new Neutron flow.

Test plan

Unit tests provided.

cc @robert-kalmar @JakeStevens @digantdesai @rascani

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19753

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❌ 2 New Failures, 2 Unrelated Failures

As of commit 704dbcf with merge base b69cbcd ():

NEW FAILURES - The following jobs have failed:

• pull / android / run-emulator (gh)
  The process '/usr/local/lib/android/sdk/platform-tools/adb' failed with exit code 224
• pull / test-qnn-testsuite-linux / test-backend-linux (qnn, models) / linux-job (gh)
  Process completed with exit code 137.

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 / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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