Avoid unnecessary copies when loading LoRAs

[isidentical]

What does this PR do?

Part of #4975, along with #4976. This PR avoids redundant deep copy operations when we are loading a LoRA. The average gain (with a LoRA where network alphas are present) on top of #4976 is about 1.35x (brings down the timings from 1.9 seconds to 1.4 seconds). On top of main it is less significant but still a good win.

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[patrickvonplaten]

I think this is also already fixed in: #4994 (very sorry about not seeing this PR earlier 🙏)

[patrickvonplaten]

Closing as already part of main