Add regression tests for boolean Pauli axel rewrites

[dlyongemallo]

Description

Adds regression tests for issue #436. Tests will currently fail so this isn't intended to be merged, but rather to act as a guide for fixes.

Related issue

#436

Checklist

• I have added/updated tests (for bugfixes, please include a regression test, for new features, include new tests either to an existing test file or a new file).
• For new features: I have updated the documentation.
• All the functions I added have a docstring parsable by sphinx (for a good example see pyzx.extract.extract_circuit).
• I have added an entry to CHANGELOG.md describing my change.