ONNX Runtime Needed for RetinaNet Tests

[ericspod]

Describe the bug
RetinaNet seems to require the onnxruntime package to export and verify the network. This doesn't seem to be the case for other networks. This causes tests to hang with a the reference ONNX runtime getting stuck here.

To Reproduce
Steps to reproduce the behavior:

1. Setup a MONAI environment without onnxruntime
2. Run PYTHONPATH=. python -m unittest tests.apps.detection.networks.test_retinanet.TestRetinaNet.test_onnx_1

Expected behavior
The test should pass.

Environment

Ensuring you use the relevant python executable, please paste the output of:

================================
Printing MONAI config...
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MONAI version: 1.5.0+16.g90b40de1.dirty
Numpy version: 2.3.1
Pytorch version: 2.6.0+cu124
MONAI flags: HAS_EXT = False, USE_COMPILED = False, USE_META_DICT = False
MONAI rev id: 90b40de1a6e3b6b902d0854b0561319faf69181f
MONAI __file__: /home/<username>/workspace/monai/MONAI_mine/monai/__init__.py

Optional dependencies:
Pytorch Ignite version: 0.4.11
ITK version: 5.4.4
Nibabel version: 5.3.2
scikit-image version: 0.25.2
scipy version: 1.16.0
Pillow version: 11.3.0
Tensorboard version: 2.19.0
gdown version: 5.2.0
TorchVision version: 0.21.0+cu124
tqdm version: 4.67.1
lmdb version: 1.7.2
psutil version: 7.0.0
pandas version: 2.3.1
einops version: 0.8.1
transformers version: NOT INSTALLED or UNKNOWN VERSION.
mlflow version: 3.1.1
pynrrd version: 1.1.3
clearml version: 2.0.2

For details about installing the optional dependencies, please visit:
    https://docs.monai.io/en/latest/installation.html#installing-the-recommended-dependencies


================================
Printing system config...
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System: Linux
Linux version: Ubuntu 24.04.2 LTS
Platform: Linux-6.11.0-26-generic-x86_64-with-glibc2.39
Processor: x86_64
Machine: x86_64
Python version: 3.12.11
Process name: python
Command: ['python', '-c', 'import monai; monai.config.print_debug_info()\n']
Open files: [popenfile(path='/home/localek10/.vscode-server/data/logs/20250809T150705/remoteagent.log', fd=22, position=856, mode='a', flags=33793), popenfile(path='/home/localek10/.vscode-server/data/logs/20250809T150705/ptyhost.log', fd=23, position=2102, mode='a', flags=33793), popenfile(path='/home/localek10/.vscode-server/data/logs/20250809T150705/remoteTelemetry.log', fd=25, position=0, mode='a', flags=33793)]
Num physical CPUs: 8
Num logical CPUs: 16
Num usable CPUs: 16
CPU usage (%): [3.8, 3.8, 3.8, 3.8, 3.8, 3.8, 3.8, 4.3, 3.8, 3.8, 3.8, 3.8, 3.8, 3.8, 99.5, 3.8]
CPU freq. (MHz): 819
Load avg. in last 1, 5, 15 mins (%): [0.0, 1.1, 3.6]
Disk usage (%): 79.9
Avg. sensor temp. (Celsius): UNKNOWN for given OS
Total physical memory (GB): 62.7
Available memory (GB): 56.2
Used memory (GB): 5.7

================================
Printing GPU config...
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Num GPUs: 2
Has CUDA: True
CUDA version: 12.4
cuDNN enabled: True
NVIDIA_TF32_OVERRIDE: None
TORCH_ALLOW_TF32_CUBLAS_OVERRIDE: None
cuDNN version: 90100
Current device: 0
Library compiled for CUDA architectures: ['sm_50', 'sm_60', 'sm_70', 'sm_75', 'sm_80', 'sm_86', 'sm_90']
GPU 0 Name: NVIDIA TITAN X (Pascal)
GPU 0 Is integrated: False
GPU 0 Is multi GPU board: False
GPU 0 Multi processor count: 28
GPU 0 Total memory (GB): 11.9
GPU 0 CUDA capability (maj.min): 6.1
GPU 1 Name: NVIDIA GeForce GTX 980
GPU 1 Is integrated: False
GPU 1 Is multi GPU board: False
GPU 1 Multi processor count: 16
GPU 1 Total memory (GB): 3.9
GPU 1 CUDA capability (maj.min): 5.2