* MPICH support

* MPICH changes

* MPICH changes

* MPICH changes

* MPICH changes

* accelerator runtime modifications

* Accelerator runtime changes

* Accelerator runtime modifications

* Remove redundant print from single node

* Move hostfile to tmp

* Code cleanup for MPICH class

* Code cleanup, rm whitespace

* Removing mpiexec environment check details

* Not needed tmp hostfile as pass directly

* Remove debugging comments

* rm print statement

* Revert comm changes as WA not needed

* Use MPICHRunner name for class

* Use MPICHRunner as class name

* No need to use args.force_multi and args.launcher .

This should be set in deepspeedexamples gpt-3.6b .sh script as:
$launcher=MPICH
run_cmd=" deepspeed  --hostfile=${hostfile_ds}  --num_nodes ${NUM_WORKERS} --num_gpus ${NUM_GPUS_PER_WORKER} --launcher=${launcher} --force_multi pretrain_gpt2.py $@ ${gpt_options}"

* Adhere to code pattern

* Rm empty lines in MPICHRunner class

* Uncomment check for num nodes and workers when used hostfile_deepspeed in gpt-3.6b.sh

* pass MPICH hostfile through launcher_args in gpt-3.6b.sh

* Clean code and remove args hostfile

* fix merge

* fix merge

---------
Co-authored-by: NAbhilash Majumder <30946547+abhilash1910@users.noreply.github.com>

* clean up and fix format

* add ut

---------
Co-authored-by: NAbhilash Majumder <30946547+abhilash1910@users.noreply.github.com>
Co-authored-by: NAmmar Ahmad Awan <ammar.awan@microsoft.com>
Co-authored-by: NOlatunji Ruwase <olruwase@microsoft.com>