Add ZImage LoRA support and integrate into ZImagePipeline

[CalamitousFelicitousness]

What does this PR do?

Adds support for LoRA for ZImagePipeline and adds a conversion script into Diffusers format. Resolves issue #12745

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@sayakpaul

[CalamitousFelicitousness]

Tested using a simple script.

Testing script

#!/usr/bin/env python
"""Test script for ZImage LoRA support."""

import sys
sys.path.insert(0, '/home/ohiom/diffusers/src')

import torch
from diffusers import ZImagePipeline

# Paths
MODEL_PATH = "database/models/huggingface/models--Tongyi-MAI--Z-Image-Turbo/snapshots/78771b7e11b922c868dd766476bda1f4fc6bfc96"
LORA_PATH = "TechnicallyColorZ_V1.safetensors"

print("Loading ZImagePipeline...")
pipe = ZImagePipeline.from_pretrained(
    MODEL_PATH,
    torch_dtype=torch.bfloat16,
    local_files_only=True,
)
pipe.to("cuda")

print(f"Pipeline loaded. Has load_lora_weights: {hasattr(pipe, 'load_lora_weights')}")

print(f"\nLoading LoRA from {LORA_PATH}...")
pipe.load_lora_weights(LORA_PATH)
print("LoRA loaded successfully!")

# Generate an image
prompt = "t3chnic4lly vibrant 1960s close-up of a woman sitting under a tree in a blue skit and white blouse, she has blonde wavy short hair and a smile with green eyes lake scene by a garden with flowers in the foreground 1960s styl;e film She's holding her hand out there is a small smooth frog in her palm, she's making eye contact with the toad."
print(f"\nGenerating image with prompt: {prompt}")

image = pipe(
    prompt=prompt,
    num_inference_steps=8,
    guidance_scale=1.0,
    height=1024,
    width=1024,
    generator=torch.Generator(device="cuda").manual_seed(42),
).images[0]

output_path = "test_zimage_lora_output.png"
image.save(output_path)
print(f"\nImage saved to {output_path}")

[sayakpaul]

@asomoza cc