on_*_batch_transfer hooks should include a dataloader_index parameter
🚀 Feature
See title
Motivation
Users might want to do different logic based on which dataloader produced the batch in particular, as different dataloaders might contain different batch structures
Pitch
def on_*_batch_transfer(batch, dataloader_idx)
Additional context
docs: https://pytorch-lightning.readthedocs.io/en/latest/common/lightning_module.html#on-after-batch-transfer
cc: @SeanNaren @rohitgr7 @williamFalcon