Update packaging checks

[tekktrik]

The actions need to be updated to support multi-package definitions in pyproject.toml.

References:

• Allow for multiple package definitions in pyproject.toml circuitpython-build-tools#147
• Explicitly list additional packages Adafruit_CircuitPython_ImageLoad#102

[tekktrik]

I think this is the offending line - now that there can be more than top-level packages, the path needs to be built out.