Arm backend: Refactor script in prep for Ethos U backend

[wwwind]

Change-Id: I10b5714e34d70e629aa8e10ecd4b3f4d71d2aaa5

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani

[pytorch-bot]

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❌ 1 New Failure, 1 Unrelated Failure

As of commit 965cf66 with merge base 050e3b1 ():

NEW FAILURE - The following job has failed:

• pull / android / run-emulator (gh)
  adb: device offline

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-qnn-testsuite-linux / test-backend-linux (qnn, models) / linux-job (gh) (trunk failure)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

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