Fix broken default installation

[lorenzomammana]

Summary

Fix quadra not installed properly without the onnx extra, minor fixes to the documentation.

Fix quadra not handling correctly failures of ONNX mixed precision export.

Fix quadra potentially using interactive backend for matplotlib.

Type of Change

• Bug fix (non-breaking change that solves an issue)

Checklist

Please confirm that the following tasks have been completed:

• I have tested my changes locally and they work as expected. (Please describe the tests you performed.)
• I have added unit tests for my changes, or updated existing tests if necessary.
• I have updated the documentation, if applicable.
• I have installed pre-commit and run locally for my code changes.