Arm backend: Refactor setup.sh to break out vulkan

[perheld]

Broke out vulkan functions and defines into a separate script that can be sourced from setup.sh.

Signed-off-by: per.held@arm.com
Change-Id: If7b8fa503d2417e449f7f6f3d95525342470824a

cc @SS-JIA @manuelcandales @cbilgin

[pytorch-bot]

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❌ 2 New Failures

As of commit a9438b8 with merge base 8456567 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 31bd2082709f60a21104962b30b02f2ff46fb11a40acfdb76b12b8ceb9db4e4f /exec failed with exit code 1
• trunk / test-models-linux-aarch64 (qwen2_5, portable, linux.arm64.2xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t 57ef5e53fa53ccfa1b9300938cc25eb4556fa3b934fc321c9f5c7872c6398b3b /exec failed with exit code 1

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