Move Graph/ProgramBuilder to backends/test

[oscarandersson8218]

Move GraphBuilder and ProgramBuilder to backends/test to make it accessible for other backends.

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

[pytorch-bot]

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❌ 4 New Failures, 2 Cancelled Jobs

As of commit 392d88f with merge base 0112ada ():

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
• pull / test-mediatek-models-linux / linux-job (gh)
  Internal Server Error occurred while resolving "actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683". Internal Server Error occurred while resolving "actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093". Internal Server Error occurred while resolving "actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02". Internal Server Error occurred while resolving "pmeier/pytest-results-action@a2c1430e2bddadbad9f49a6f9b879f062c6b19b1". Internal Server Error occurred while resolving "pytorch/pytorch/.github/actions/setup-rocm@main"
• trunk / test-models-linux-aarch64 (phi_4_mini, portable, linux.arm64.m7g.4xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t b3405aecdbc6b9e6c94b544bb959af05feac99536a5a9e92bdc429a23a63667a /exec failed with exit code 1
• trunk / test-models-macos-cpu (w2l, xnnpack-quantization-delegation) / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• periodic / gather-models (gh)
  ##[error]The operation was canceled.
• trunk / test-mcu-cortex-m-backend / linux-job (gh)

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[oscarandersson8218]

Hi, @SS-JIA, we would like to start using Program/GraphBuilder in the backends/arm/test so I propose we move it to backends/test to make it accessible for other backends. I'm a bit unsure about the BUCK and bazel parts. Please add appropriate labels and reviewers.