Add pytest option to run FVPs in fast mode

[Erik-Lundell]

Add --fast_fvp when running pytest to enable
Also adds flag to disable visualisation for
Corstone320

Change-Id: I4a49bce7f773d805f89f0255c1c08e0c277edd58

[pytorch-bot]

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• [DomainsOnly] Jobs fail with GLIBC version not found

❌ 2 New Failures

As of commit c830fb3 with merge base eae0b04 ():

NEW FAILURES - The following jobs have failed:

• Check Labels / Check labels (gh)
  ##[error]Process completed with exit code 1.
• pull / test-llama-runner-linux (bf16, portable) / linux-job (gh)
  ##[error]An error occurred trying to start process '/usr/bin/bash' with working directory '/home/ec2-user/actions-runner/_work/executorch/executorch/pytorch/executorch'. No such file or directory

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