Implements GPU monitoring when using the MPS (macOS) compute backend

Closes #7

See merge request biosignal/software/mednet!14

Rename package from ptbench -> mednet (closes #46)

Closes #46

See merge request biosignal/software/ptbench!13

Lightning API was fixed so these can be removed.

Adds grad-cam support on classifiers

Closes #49, #51, and #31

See merge request biosignal/software/ptbench!12

Typing.Self was introduced in Python 3.11 so we cannot use it in the
3.10 pipeline.

Lightning 2.1.3 changes how checkpoints are saved, which breaks
how we handle saving and loading. This should be reverted in the
next release of lightning.