Enable ucc backend for pp [NeMo1/NeMo2]

[youngeunkwon0405]

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What does this PR do ?

This MR provides an interface to enable the UCC backend for PP communication.
To enable the UCC backend, set the following argument:

• NeMo1 interface
  training.model.pipeline_model_parallel_comm_backend=ucc

• NeMo2 interface

import nemo.collections.llm.recipes
pretrain_recipe = eval(f"nemo.collections.llm.recipes.{model_name}.pretrain_recipe")
recipe = pretrain_recipe(...)
recipe.trainer.strategy.pipeline_model_parallel_comm_backend = 'ucc'

Requires a related MCore MR (link).
Collection: [Note which collection this PR will affect]

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