INT8 Quantization and compiling for Google Coral

In case it is helpful to people, here is a repo that provides a version of YOLO v9 that can run on the Google Coral EdgeTPU device. https://github.com/dbro/frigate-detector-edgetpu-yolo9

There are two Colab notebooks that demonstrate (1) how to change the model to use ReLU6 as the activation function and then run fine-tuning, and (2) how to convert the .pt file into ONNX and then convert+quantize that to TFLite.

(1) https://colab.research.google.com/drive/1RAZqCHuDWFdFxqFpL78OVfZQvnGoM6rH?usp=sharing

(2) https://colab.research.google.com/drive/1AdFfPn1zYj86e_n2Bq3hvvNbIlyn8Vei?usp=sharing

Related issues: #388 #327