Introduce XZFaultList for tracking X and Z faults simultaneously

[sunjerry019]

Description

Expands on the idea of PureFaultSet by having a list (i.e. stable order) of coupled $X$- and $Z$-Faults on which gates such as CNOTs, H, Reset may be applied.

#690 should be merged first.

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
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[codecov]

Codecov Report

❌ Patch coverage is 94.19355% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/mqt/qecc/circuit_synthesis/faults.py	94.1%	9 Missing ⚠️

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