Describe the bug
We have a function called set_visible_devices, but I can't see it used anywhere, it's not tested, and I'm not convinced it works... I think it should be deleted.

If we set the visible device to 0 before importing monai (and therefore torch), and then requesting device 1, the following fails, as expected:

import os
os.environ['CUDA_VISIBLE_DEVICES']='0'
import torch
a=torch.rand((1), device='cuda:1')
print(a.device)

output:

RuntimeError: CUDA error: invalid device ordinal

However, when setting the device after importing monai (and therefore torch), it seems to be ignored as the following is fine:

import monai
monai.config.deviceconfig.set_visible_devices(0)
import torch
a=torch.rand((1), device='cuda:1')
print(a.device)

output:

cuda:1

I therefore don't see a scenario in which set_visible_devices can function.