[PR] Support face-parsing semantic segmentation model

[tucan9389]

face-parsing model

video source: https://www.youtube.com/watch?v=D571qZzLfX4

PR Points

• Support the face-parsing semantic segmentation model
• Support to visualize multi-class semantic segmentation output
  • Add MultitargetSegmentationTextureGenerater.swift
  • Add new multitarget_segmentation_render_target shader function in Shaders.metal

Model Info

• original model repo: https://github.com/zllrunning/face-parsing.PyTorch

Related Issues

• Support face-parsing model #12
• Support various colors in GPU live demo #13
• Support the Core ML model for iOS zllrunning/face-parsing.PyTorch#27

How to run the FaceParsing model?

1. Download the mlmodel from here
2. Import the FaceParsing.mlmodel into SemanticSegmentation-CoreML>mlmodel folder of the project
3. Change the minimum iOS version to 14.0+
4. Change the model class from DeepLabV3() to FaceParsing() in LiveImageViewController.swift or LiveMetalCameraViewController.swift
5. Build & run the project on the real device

[tucan9389]

@jsharp83 Could you review my pull request for Metal codes?