adding bias_dropout_add_fusion option for BERT
# What does this PR do ?

Adding an option to disable `bias_dropout_add_fusion`, same as for GPT model [here](https://github.com/NVIDIA/NeMo/blob/455d2dfb3479cd30a7857db3c2e2864a921488b8/nemo/collections/nlp/models/language_modeling/megatron_gpt_model.py#L362)

**Collection**: Language Modeling -> BERT

# Changelog 
- `bert_model.py:188` - adding the flag to the `bert_model` constructor
- `bert_model.py:236` - passing the flag to the `language_model` creation
- `megatron_bert_model.py:184` - passing the flag to the `bert_model` based on config

# Usage
* `bias_dropout_add_fusion: <BOOLEAN>` can now be set in BERT model config

# 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.

# Additional Information
* Related to # (issue)
