✨ Switch to mqt-core Python package

[burgholzer]

Description

This is an alternative to #355 and marks the final transition to the mqt-core Python package. See #355 and #352 for some history on this topic.

In addition to directly using the MQT Core Python package, this PR makes Qiskit an optional dependency of MQT QCEC. All core functionality is now covered MQT-internally.

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[codecov]

Codecov Report

Attention: Patch coverage is 98.76543% with 2 lines in your changes missing coverage. Please review.

Project coverage is 96.1%. Comparing base (379c211) to head (0987b8f).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/mqt/qcec/parameterized.py	97.0%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #432     +/-   ##
=======================================
+ Coverage   95.8%   96.1%   +0.3%     
=======================================
  Files         39      40      +1     
  Lines       1837    1877     +40     
  Branches     225     224      -1     
=======================================
+ Hits        1760    1804     +44     
+ Misses        77      73      -4     

Flag	Coverage Δ
cpp	95.9% <ø> (-0.1%)	⬇️
python	96.4% <98.7%> (+1.5%)	⬆️

Files with missing lines	Coverage Δ
src/mqt/qcec/__init__.py	100.0% <100.0%> (ø)
src/mqt/qcec/_compat/optional.py	100.0% <100.0%> (ø)
src/mqt/qcec/compilation_flow_profiles.py	98.1% <100.0%> (+1.3%)	⬆️
src/mqt/qcec/configuration.py	100.0% <100.0%> (ø)
src/mqt/qcec/verify.py	100.0% <100.0%> (ø)
src/mqt/qcec/verify_compilation_flow.py	100.0% <100.0%> (ø)
src/mqt/qcec/parameterized.py	94.5% <97.0%> (-0.4%)	⬇️

... and 4 files with indirect coverage changes

[burgholzer]

Alright, some progress.

The new ubuntu-24.04-arm runners fail due to a uv error that will probably be fixed soonish (a PR is open at astral-sh/uv#10697).

The Ubuntu 22.04 builds fail because pybind decides that the compiled version of mqt-core that comes from PyPI is not binary-compatible with the mqt-qcec extension being compiled.
Hence, it does not recognize the qc::QuantumComputation class. This has been addressed in pybind/pybind11#5439 which, unfortunately, has not been released yet.
We can work around this for now by compiling mqt-core from source, although that should not be a long term solution.

[burgholzer]

A year-long odyssey is finally coming to an end. All the tests are green, all issues resolved. I see no reason for leaving this lying around anymore. Especially, since we cannot update to more recent versions of MQT Core without this PR.
I will probably cut a pre-release once this merged in order to battle-test the solution.