[Feature]: support FP8 communication in DDP, FSDP, Gemini (#5928)

* support fp8_communication in the Torch DDP grad comm, FSDP grad comm, and FSDP params comm

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* implement communication hook for FSDP params all-gather

* added unit test for fp8 operators

* support fp8 communication in GeminiPlugin

* update training scripts to support fsdp and fp8 communication

* fixed some minor bugs observed in unit test

* add all_gather_into_tensor_flat_fp8

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* add skip the test if torch < 2.2.0

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* add skip the test if torch < 2.2.0

* add skip the test if torch < 2.2.0

* add fp8_comm flag

* rebase latest fp8 operators

* rebase latest fp8 operators

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

examples/language/gpt/hybridparallelism/finetune.py

@@ -212,7 +212,7 @@ def main():
     if args.plugin == "torch_ddp_fp16":
         booster_kwargs["mixed_precision"] = "fp16"
     if args.plugin.startswith("torch_ddp"):
-        plugin = TorchDDPPlugin()
+        plugin = TorchDDPPlugin(fp8_communication=args.use_fp8_comm)
     elif args.plugin == "gemini":
         plugin = GeminiPlugin(initial_scale=2**5)
     elif args.plugin == "low_level_zero":