Add TFLite conversion to status report?

[rgov]

I ran an experiment to evaluate how much of the ONNX Model Zoo can be converted to TFLite. Here are my results:

Value	Count
Models	39
Total	168
✔️ Passed	123
⚠️ Limitation	9
❌ Failed	36
➖ Skipped	0

Here, "Passed" means that the model could be converted to TFLite using either the built-in TFLite ops only, or additionally select TF ops. I did not attempt to run the resulting models though that would be a good improvement.

Also attached to the Gist is my hacky patch to perform the testing. If it would be valuable, we could polish this up and add it to the test reports generated by CI. However, the conversion from TF to TFLite does not really involve this project.