Running `scripts/run_pipeline.py` torch and semantic kitti results in pickling error

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D-ML/issues).
- [X] I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `main` branch).

### Describe the issue

trying to run the training pipeline with torch, RandLaNet and semantic kitti results in pickling error:
`python scripts/run_pipeline.py torch -c ml3d/configs/randlanet_semantickitti.yml --dataset_path //semantic_kitti/`

### Steps to reproduce the bug

```python
`$python scripts/run_pipeline.py torch -c ml3d/configs/randlanet_semantickitti.yml --dataset_path //semantic_kitti/`
```

### Error message

```
regular arguments
backend: gloo
batch_size: null
cfg_dataset: null
cfg_file: ml3d/configs/randlanet_semantickitti.yml
cfg_model: null
cfg_pipeline: null
ckpt_path: null
dataset: null
dataset_path: /media/nikste/SSD_030_06/semantic_kitti/
device: cuda
device_ids:
- '0'
framework: torch
host: localhost
main_log_dir: null
max_epochs: null
mode: null
model: null
node_rank: 0
nodes: 1
pipeline: SemanticSegmentation
port: '12355'
seed: 0
split: train

extra arguments
{}

open3d-ml/venv/lib/python3.10/site-packages/torch/cuda/__init__.py:107: UserWarning: CUDA initialization: CUDA unknown error - this may be due to an incorrectly set up environment, e.g. changing env variable CUDA_VISIBLE_DEVICES after program start. Setting the available devices to be zero. (Triggered internally at ../c10/cuda/CUDAFunctions.cpp:109.)
return torch._C._cuda_getDeviceCount() > 0
INFO - 2024-02-17 19:11:23,311 - semantic_segmentation - DEVICE : cpu
INFO - 2024-02-17 19:11:23,311 - semantic_segmentation - Logging in file : ./logs/RandLANet_SemanticKITTI_torch/log_train_2024-02-17_19-11-23.txt
INFO - 2024-02-17 19:11:23,332 - semantickitti - Found 19130 pointclouds for train
INFO - 2024-02-17 19:11:24,468 - semantickitti - Found 4071 pointclouds for validation
INFO - 2024-02-17 19:11:24,723 - semantic_segmentation - Initializing from scratch.
INFO - 2024-02-17 19:11:24,724 - semantic_segmentation - Writing summary in train_log/00002_RandLANet_SemanticKITTI_torch.
INFO - 2024-02-17 19:11:24,724 - semantic_segmentation - Started training
INFO - 2024-02-17 19:11:24,724 - semantic_segmentation - === EPOCH 0/100 ===
training: 0%| | 0/4783 [00:00
sys.exit(main())
File "open3d-ml/scripts/run_pipeline.py", line 192, in main
pipeline.run_train()
File "open3d-ml/venv/lib/python3.10/site-packages/open3d/_ml3d/torch/pipelines/semantic_segmentation.py", line 405, in run_train
for step, inputs in enumerate(tqdm(train_loader, desc='training')):
File "open3d-ml/venv/lib/python3.10/site-packages/tqdm/std.py", line 1182, in __iter__
for obj in iterable:
File "open3d-ml/venv/lib/python3.10/site-packages/torch/utils/data/dataloader.py", line 441, in __iter__
return self._get_iterator()
File "open3d-ml/venv/lib/python3.10/site-packages/torch/utils/data/dataloader.py", line 388, in _get_iterator
return _MultiProcessingDataLoaderIter(self)
File "open3d-ml/venv/lib/python3.10/site-packages/torch/utils/data/dataloader.py", line 1042, in __init__
w.start()
File "/usr/lib/python3.10/multiprocessing/process.py", line 121, in start
self._popen = self._Popen(self)
File "/usr/lib/python3.10/multiprocessing/context.py", line 224, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "/usr/lib/python3.10/multiprocessing/context.py", line 300, in _Popen
return Popen(process_obj)
File "/usr/lib/python3.10/multiprocessing/popen_forkserver.py", line 35, in __init__
super().__init__(process_obj)
File "/usr/lib/python3.10/multiprocessing/popen_fork.py", line 19, in __init__
self._launch(process_obj)
File "/usr/lib/python3.10/multiprocessing/popen_forkserver.py", line 47, in _launch
reduction.dump(process_obj, buf)
File "/usr/lib/python3.10/multiprocessing/reduction.py", line 60, in dump
ForkingPickler(file, protocol).dump(obj)
AttributeError: Can't pickle local object 'SemSegRandomSampler.get_point_sampler.._random_centered_gen'
```

### Expected behavior

_No response_

### Open3D, Python and System information

```markdown
- Operating system: ubuntu
```

### Additional information

_No response_