Unloading multiple loras: norms do not return to their original values

When unloading from multiple loras on flux pipeline, I believe that the norm layers are not restored [here](https://github.com/huggingface/diffusers/blob/464374fb87610c53b2cf81e08d3df628fada3ce4/src/diffusers/loaders/lora_pipeline.py#L1575).

Shouldn't we have:

```python
if len(transformer_norm_state_dict) > 0:
original_norm_layers_state_dict = self._load_norm_into_transformer(
transformer_norm_state_dict,
transformer=transformer,
discard_original_layers=False,
)
if not hasattr(transformer, "_transformer_norm_layers"):
transformer._transformer_norm_layers = original_norm_layers_state_dict
```

Start in src/diffusers/loaders/lora_pipeline.py around line 1575 and trace how transformer norm state is saved and restored when unloading multiple LoRAs from the Flux pipeline. Reproduce the unload sequence and verify that the norm layers return to their original values.

Scritto dal modello di indicizzazione a partire dal testo della issue.