Adopt the standalone OnnxOcr from upstream PR #5893 (381bb8d05,
by Horizon101011), which vendors cnocr's pure-Python pipeline so
the ONNX path loads no mxnet at runtime. Backend is selected via
deploy config, keeping onnxruntime a standard dependency and onnx
the default.
Co-authored-by: Horizon101011 <43370844+Horizon101011@users.noreply.github.com>