Conversion for LLM class loading with VLM ckpt

[zucchini-nlp]

What does this PR do?

fixes #45216 and #45310 and #45313

TBH load-save-load works for the model on main branch which is why the tests are not failing, it is only that the saved sd is completely weird and incorrect. Also smth when deepspeed loading, but I didn't check really

This works when from_pretrained just because we replace all matches with original_key.replace thus the whole language_model.language_model.language_model part is replaced

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: gemma3n, qwen3_5, qwen3_5_moe

[HuggingFaceDocBuilderDev]

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