Simplification of Plugin development - Use Spandrei

[RobBW]

The code for Chainner has recently been restructured an a library called Spandrei created.

Spandrel is a library for loading and running pre-trained PyTorch models. It automatically detects the model architecture and hyperparameters from model files, and provides a unified interface for running models.

It is available from: https://github.com/chaiNNer-org/spandrel

This might be helpful to developers of Gimp-ML plugins