Expose DS-inference and ZeRO-inference configs to user

[jeffra]

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After #25 is complete we want to expose all DS-inference configs (https://deepspeed.readthedocs.io/en/latest/inference-init.html#deepspeed.init_inference) and ZeRO inference configs in the MII config dictionary.

[cli99]

ZeRO inference currently takes the general deepspeed config json path. Do we want to expose DS-inference config in the deepspeed config file as well?

[jeffra]

Good point @cli99, I forgot that the zero-inference PR adds ds_config as a MII deploy argument. Let's leave it like that for now, but maybe we can merge some of these configs in the near future.