[Big deprecation] Introduces a DataLoaderConfig

[muellerzr]

What does this PR do?

As we prepare for 1.0.0, this PR introduces a large deprecation to some of the arguments in the Accelerator, wherein all arguments related to the configuration of the DataLoader are now sent through the DataLoaderConfig. After this PR is merged, we will aim for a 2-release gap between this and 1.0.0 (by May at the latest), as this is a very large (and potentially scary) change for users.

The reasoning is to make it easier for integrations like transformers (and in the future accelerate in general) to configure seperate entities related to more config-heavy items in the accelerator more manageable, and leave the base params in the Accelerator (without config) to be true core important items.

Mapping of old to new:

-accelerator = Accelerator(split_batches=True, dispatch_batches=True)
+dl_config = DataLoaderConfig(split_batches=True, dispatch_batches=True)
+accelerator = Accelerator(dataloader_config=dl_config)

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@SunMarc @BenjaminBossan

[HuggingFaceDocBuilderDev]

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[BenjaminBossan]

In general, this looks good. I have some minor comments and then a discussion about detecting the deprecated arguments, where I'm unsure what the best course of action is. Please take a look.

[BenjaminBossan]

I found another potential issue with backwards compatibility, please check.

[BenjaminBossan]

Looks good now from my side, thanks for working on this refactor.

[SunMarc]

Thx for your work !

[SunMarc]

We could maybe use logger.warning so that users have more control of their logs.

[muellerzr]

In this case we don't want them to mute that as these deprecations aren't ones that will exist for many, many months. They'll exist for a very short (relative) time. We have this for the other 1.0 warnings as well :)

(Just checked, same with transformers)

[SunMarc]

nice !