fix the warning torch_dtype is deprecated

[msdsm]

Motivation

When users load pipelines like QwenImageEditPipeline with the torch_dtype parameter, they see a deprecation warning from the Transformers library. However, changing to dtype (as the warning suggests) causes errors because diffusers' from_pretrained doesn't accept dtype as a parameter.

This creates a confusing user experience where:

1. Users see a deprecation warning
2. Following the warning's advice breaks their code
3. There's no way to avoid the warning without modifying the diffusers library

Solution

This PR internally converts torch_dtype to dtype when loading Transformers models (transformers >= 4.20.0), while keeping torch_dtype for diffusers models and other components.

Fixes #12840

Who can review?

• Pipelines and pipeline callbacks: @yiyixuxu and @asomoza

[DN6]

Think we would also need to check if transformers version is greater than 4.56.0.

[msdsm]

@DN6 Thanks for the review! I've updated the code to check for transformers version >= 4.56.0 before using the dtype parameter.

[DN6]

Thanks @msdsm 👍🏽

[HuggingFaceDocBuilderDev]

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[DN6]

@bot /style

[msdsm]

@DN6 Linting errors have been fixed. CI is waiting for workflow approval.