Make MegatronBert converter compatible with latest megatron code
Author: MagiaSN
Pull request: yes

# What does this PR do?

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The attention parameters in latest megatron code are renamed to `self_attention.*`, (see https://github.com/NVIDIA/Megatron-LM/blob/e156d2fea7fc5c98e645f7742eb86b643956d840/megatron/model/transformer.py#L429), we should also change them in the megatron converter code.

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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @LysandreJik

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Hey, thank you for your PR! It was superseded by the following PR: https://github.com/huggingface/transformers/pull/15820

Thanks again!

> Hey, thank you for your PR! It was superseded by the following PR: #15820
> 
> Thanks again!

Very good, sorry for missing it :)