Arm backend: Refactor setup.sh to break out fvp installation

[perheld]

Broken out the fvp installation into a separate script handling only that part. No functional change.

Change-Id: I8accf263ae8617dc5679a6b4e21e9331dffdda34
Signed-off-by: per.held@arm.com

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

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❌ 3 New Failures, 1 Cancelled Job, 1 Unrelated Failure

As of commit 9599d09 with merge base 8ba92a9 ():

NEW FAILURES - The following jobs have failed:

• Apple / build-demo-ios / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 65
• Build documentation / build (buck2) / Build doc (gh)
  At least one of the pre-conditions you specified did not hold
• pull / test-llama-runner-qnn-linux (fp32, qnn_8a8w, qnn) / linux-job (gh)
  RuntimeError: Command docker exec -t 87c4dabd888fea22cba84a120912c2d15acd7c44f71f593aac35a3d1fb1acc2d /exec failed with exit code 1

CANCELLED JOB - The following job was cancelled. Please retry:

• trunk / test-models-macos-cpu (mv3, xnnpack-quantization-delegation) / macos-job (gh)
  ##[error]The operation was canceled.

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

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

• pull / unittest-nxp-neutron / linux-job (gh) (trunk failure)
  test_split_group_convolution__applied_by_default

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[zingo]

Test fails unrelated