[Other] Update old Api to new ones (#861)

* Update keypointdetection result docs

* Update im.copy() to im in examples

* Update new Api, fastdeploy::vision::Visualize to fastdeploy::vision

* Update SwapBackgroundSegmentation && SwapBackgroundMatting to SwapBackground

* Update README_CN.md

* Update README_CN.md

README_CN.md

@@ -164,7 +164,7 @@ int main(int argc, char* argv[]) {
   vision::DetectionResult res;
   model.Predict(im, &res);
 
-  auto vis_im = vision::Visualize::VisDetection(im, res, 0.5);
+  auto vis_im = vision::VisDetection(im, res, 0.5);
   cv::imwrite("vis_image.jpg", vis_im);
   return 0;
 }