Arm backend: ArmTester support testing with portable ops

[zingo]

Summary

This will enable model testing where some ops are not fully delegated, like done in the backend flow test suite.

This will also extend the FVP timeout to 10 min for backend flows and increase allocation pool to 80MB to make it possible to tests larger models.

Test plan

Arm backend suite test will tests this.

cc @freddan80 @per @oscarandersson8218 @digantdesai

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15278

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❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• AWS was down, GHA infrastructure effected / recovering

❌ 7 New Failures, 2 Unrelated Failures

As of commit 6baf7e2 with merge base fedaa2d ():

NEW FAILURES - The following jobs have failed:

• pull / android / run-emulator (gh)
  The process '/usr/bin/sh' failed with exit code 255
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t eed432ffdd600f9be462b2b8bf3399361045c47851ff5d08862f24e381a5e3c2 /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 6f178275eb9471e72c652f22b93ae492dc3d2cdd30e101955ac1c80d11b911aa /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t f7a1a8282959a74de14331a56eb8fc1313906b88d3bf85c65873e13e779bf7f7 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 2561b175ceee2ef7f31dcefb3c2dd3b2591852cd24cfa96c6aaa9bc282811fd3 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t 47ec5d91a636de5aaa6f6e7e0939aafcb5c5a8014fc65087f9a832cdbeca0da8 /exec failed with exit code 2
• Test Metal Backend / export-voxtral-metal-artifact / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 2

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 / linux / linux-job (gh) (trunk failure)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)

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