Distributed optimizer support for BERT
# What does this PR do ?

Add support for the distributed Adam optimizer to BERT.

**Collection**: NLP

# Changelog 
- Add support for the Apex distributed Adam optimizer to BERT

# Usage

Set the optimizer to `distributed_fused_adam` in the config file:

https://github.com/NVIDIA/NeMo/blob/79a22eaee0813d5a0e4dc82ebd4a43071399c899/examples/nlp/language_modeling/conf/megatron_bert_config.yaml#L118

# Before your PR is "Ready for review"
**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

Pinging @shanmugamr1992.

# Additional Information
* Depends on https://github.com/NVIDIA/NeMo/pull/5293.
* BERT distopt support in this PR is basically identical to GPT and T5 distopt support in https://github.com/NVIDIA/NeMo/pull/5236.
