Enhance HfArgumentParser with Dict command-line parser

[xu-song]

Feature request

Enhance HfArgumentParser with Dict command-line parser

Motivation

There are many arguments with dict typing, such as lr_scheduler_kwargs, gradient_checkpointing_kwargs.

transformers/src/transformers/training_args.py

Line 806 in 6cdbd73

lr_scheduler_kwargs: Optional[Dict] = field(

transformers/src/transformers/training_args.py

Line 1255 in 6cdbd73

gradient_checkpointing_kwargs: Optional[dict] = field(

It is possible to pass dict arguments through json_file or yaml_file.
But it does not work in command-line.

Your contribution

TBD

[amyeroberts]

cc @pacman100 @muellerzr