✨ switch to mqt-core Python package

[burgholzer]

Description

This PR is a best-of extraction from #352 and switches the project to use the newly developed mqt-core Python package.
Due to the use of FetchContent, any Python package build will only require the mqt-core package as a build and runtime dependency and won't have to rely on the git submodule (or a fetched version of mqt-core) any more.
Any regular C++ build will use the FetchContent CMake module. This logic could probably be improved a little bit so that the submodule is used whenever it has been properly cloned.

The change brings a range of advantages:

• Uses the new load function of mqt-core that allows to load any supported circuit format as input and has better handling for Qiskit QuantumCircuit objects.
• Allows to directly feed QASM strings as inputs to the verification methods
• Completely eliminates the Qiskit dependency from the symbolic EC code as everything can be handled natively with mqt-core now.
• Simplifies the interfaces of the QCEC Python bindings

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: 2 lines in your changes are missing coverage. Please review.

Comparison is base (8a5779a) 96.4% compared to head (b555c9f) 96.2%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #355     +/-   ##
=======================================
- Coverage   96.4%   96.2%   -0.2%     
=======================================
  Files         34      34             
  Lines       1753    1749      -4     
  Branches     215     215             
=======================================
- Hits        1690    1684      -6     
- Misses        63      65      +2     

Flag	Coverage Δ
cpp	96.0% <ø> (-0.2%)	⬇️
python	97.1% <97.2%> (-0.1%)	⬇️

Files	Coverage Δ
src/mqt/qcec/__init__.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% <ø> (ø)
src/mqt/qcec/parameterized.py	94.5% <96.8%> (-0.4%)	⬇️

... and 2 files with indirect coverage changes

[github-actions]

Cpp-Linter Report ⚠️

Some files did not pass the configured checks!

clang-tidy reports: 4 concern(s)

• include/mqt-qcec/checker/EquivalenceChecker.hpp

  include/mqt-qcec/checker/EquivalenceChecker.hpp:42:33: warning: [cppcoreguidelines-avoid-const-or-ref-data-members]

  member 'qc1' of type 'const qc::QuantumComputation &' is a reference

    const qc::QuantumComputation& qc1;
                                  ^

  include/mqt-qcec/checker/EquivalenceChecker.hpp:43:33: warning: [cppcoreguidelines-avoid-const-or-ref-data-members]

  member 'qc2' of type 'const qc::QuantumComputation &' is a reference

    const qc::QuantumComputation& qc2;
                                  ^

• include/mqt-qcec/checker/dd/applicationscheme/SequentialApplicationScheme.hpp

  include/mqt-qcec/checker/dd/applicationscheme/SequentialApplicationScheme.hpp:26:21: warning: [cppcoreguidelines-avoid-const-or-ref-data-members]

  member 'gates1' of type 'const std::size_t' (aka 'const unsigned long') is const qualified

    const std::size_t gates1;
                      ^

  include/mqt-qcec/checker/dd/applicationscheme/SequentialApplicationScheme.hpp:27:21: warning: [cppcoreguidelines-avoid-const-or-ref-data-members]

  member 'gates2' of type 'const std::size_t' (aka 'const unsigned long') is const qualified

    const std::size_t gates2;
                      ^

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