Fixes(sdxl): fix some bugs in mindone.diffusers sdxl training

[townwish4git]

What does this PR do?

Fixes # (issue)

Fixed bugs in mindone.diffusers sdxl training to support:

• distributed training
• timesteps bias sampling
• save/resume checkpoint
• snr gamma loss weighting
• RandomCrop data preprocessing

Masked option 'bf16' for amp as MindSpore has issues with dtype inference in that case

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [ ] Did you read the contributor guideline?
• [ ] Did you make sure to update the documentation with your changes? E.g. record bug fixes or new features in What's New. Here are the documentation guidelines
• [ ] Did you build and run the code without any errors?
• [ ] Did you report the running environment (NPU type/MS version) and performance in the doc? (better record it for data loading, model inference, or training tasks)
• [ ] Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag members/contributors who may be interested in your PR.

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