[V3] convert Canny node to V3 schema

[bigcat88]

MyTestNode was created only to test that nothing breaks for community.

Sources of MyTestNode node:

@classmethod
def execute(cls, image, low_threshold, high_threshold) -> io.NodeOutput:
    from nodes import NODE_CLASS_MAPPINGS

    canny2 = NODE_CLASS_MAPPINGS["Canny"]()  # community nodes create Canny node likes this
    return canny2.detect_edge(
        low_threshold=low_threshold,
        high_threshold=high_threshold,
        image=image,
    )  # and calls like this

Example of community usage:

https://github.com/nunchaku-tech/ComfyUI-nunchaku/blob/90fb8ccf455a4bffa5fb832b84e54951d1e2949d/tests/scripts/nunchaku-flux1-canny.py#L157-L162