Moved code to lightning

See merge request biosignal/software/ptbench!4

Tbx11k

See merge request biosignal/software/ptbench!5

As the criterion is not part of the model but instead a hyperparameter
due to the use of configuration files, it is not moved to the GPU if
selected as a device. We therefore manually move the criterion to the proper
device, which is bad practice when using lightning but works.

pytorch-lightning is in the process of changing their package names to
simply lightning.

The obects.inv file from lightning's documentation is missing a lot of
methods, raising errors when building with sphinx. Problematic methods
have been added to the extras.txt and encoded into extras.inv

Auto intersphinx would try to access "https://lightning.ai/lightning-docs/objects.inv" and would be
redirected to "https://lightning.ai/docs/app/stable/objects.inv" instead
of "https://lightning.ai/docs/pytorch/stable/objects.inv"

The CUDA_VISIBLE_DEVICES environement variable is set if a device is
specified or we raise an error if it has not been set.
Code for accelerator handling has been moved to its own utils script.