Remove unused args and methods from GenericTrainingManager

lastest_batch
total_batch
grad_acc_step
latest_train_metrics
latest_valid_metrics
curriculum_info
phase
max_mem_usage_by_epoch
losses
lr_values
cleanup()
update_curriculum()
add_checkpoint_info(...)

All of these args/methods are never used in the code and should be removed. See https://gitlab.com/teklia/atr/dan/-/blob/2adb6ba8e9f7698b3f7968292a87c6dde920f42b/dan/manager/training.py