* replace init_ddp_connection for index init
* style
* add finetune test
* add test data
* move generate tensors to device
* add test on EM metric
* style
* allow multi process test
* keep gloo process group for retrieval
* add multi-gpu test
* use custom accelerator
* clean test finetune
* minor
* style
* style
* typo
* use python call instead of imported main fumction
* return_dict fix in modeling_rag
* use float32 in retrieval
* store as float32 as well in the custom knowledge dataset example
* style
* rename to finetune_rag
* style
* update readme
* rename utils and callbacks to utils_rag and callbacks_rag
* fix test
* patrick's comments
* generate dummy data in the finetue test script
* remove dummy data files
* style
