Moved code to lightning

Updating codebase to make use of pytorch-lightning

• Main train/valid loops are handled by lightning
• Removed device-handling code
• Each model implements its own train/valid/predict steps
• Updated config files for use with lightning
• Using lightning checkpointing and logging callbacks
• Updated DeviceMonitor to be compatible with lightning

src/ptbench/configs/models/pasa.py

@@ -28,5 +28,3 @@ criterion_valid = BCEWithLogitsLoss(pos_weight=empty(1))
 
 # model
 model = PASA(criterion, criterion_valid, optimizer, optimizer_configs)
-model.criterion = criterion
-model.criterion_valid = criterion_valid