Add effective_region_mask for ipadapter [API]

[huchenlei]

Closes #2451.

• Add tests

Currently only API support. GUI support will come later.

API usage:

        payload_overrides={
            "prompt": "(masterpiece: 1.3), (highres: 1.3), best quality, (2girls: 1.3)",
            "width": 768,
            "height": 512,
            "steps": 20,
        },
        unit_overrides=[
            {
                "module": "ip-adapter-auto",
                "model": get_model("ip-adapter_sd15"),
                "image": girl_img,
                "effective_region_mask": mask_left,
            },
            {
                "module": "ip-adapter-auto",
                "model": get_model("ip-adapter_sd15"),
                "image": realistic_girl_face_img,
                "effective_region_mask": mask_right,
            },
        ]

Input image 1

Input image 2

Result