Launch mpirun from accelerate launch for multi-CPU training (#2493)
* Update accelerate config and launch to abstract out mpirun
* Fix var
* Documentation updates, updating the launch script to work with other MPI programs, and fixing the nlp example when using IPEX
* Style fixes
* Add a test
* Style fixes
* Formatting fix
* Updates based on review feedback.
* Remove model.train()
* Doc update
* Update doc regarding the accelerate config with the old method of mpirun and accelerate
* Fix typo in comment
* Quality and test updates
* Updates based on review feedback
* Quality fix
* Fix mock patch path
* Updates based on review feedback
* Quality fixes