♻️ Refactor Packaging and CI

[burgholzer]

Description

This PR brings a major refactoring for the overall Python packaging as well as the CI employed in the project.

Packaging

We are (finally) moving away from setuptools and towards modern scikit-build-core (https://scikit-build-core.readthedocs.io/)
This brings many advantages such as

• truly editable installs that also include the C++ part; this implies incredibly fast rebuilds that can be further improved by installing ccache.
• completely eliminates the setup.py (and the MANIFEST.in) file and all custom build code that was required previously.

As part of this change, we adopt the established best practice of a src-layout for the Python package. This implies that the Python package no longer lives in the main package directory, but is moved to src/mqt/....
This avoids several pitfalls when working with Python packages and makes the overall handling way easier.

This also means there is no direct build-time dependency on cmake and ninja anymore as this is automatically handled by scikit-build-core on demand.

As part of this rewrite, several nox sessions are also updated

CI

MQT Core has introduced reusable workflows in

• 🧑‍💻 Extensive and Reusable CI/CD Setup mqt-core#396

These have been further refined in

• 🚸 Make reusable workflows more generic mqt-core#407

Overall, this allows to

• remove almost all workflow files of this repository
• eliminate a lot of maintenance required in this repository to keep up with the latest best practices
• rely on dependabot for workflow updates once MQT Core has settled enough so that it follows proper versioning and we can use tags for the workflows here instead of @main

while at the same time:

• having automatic change detection and only triggering jobs that are really necessary; with a single pass check that can be used for branch protection
• setting up ccache for all supported workflow jobs which greatly improves compilation times
• setting up mold as a better linker under linux
• splitting jobs into as many subjobs as possible and feasible to distribute work
• automatically creating wheels for all supported platforms (including exotic platforms that need emulation) and Python versions using PyPI trusted publishing
• enabling automatic retries for flaky jobs such as MSVC builds or coverage uploads
• enabling automatic build parallelization via using Ninja wherever suitable
• running an automatic workflow using the minimal versiosn for all Python dependencies to guarantee compatibility

As a nice side effect, the new CI has revealed two bugs in the heuristic mapper. One where the single-qubit gates could not be placed properly and one where the output permutation inference accessed arrays out of bounds. Both issues have subsequently been fixed.

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.

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[codecov]

Codecov Report

Merging #366 (c9744a6) into main (fbc1e03) will decrease coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main    #366     +/-   ##
=======================================
- Coverage   92.3%   92.2%   -0.1%     
=======================================
  Files         44      44             
  Lines       4155    4162      +7     
  Branches     699     701      +2     
=======================================
+ Hits        3837    3841      +4     
- Misses       318     321      +3     

Flag	Coverage Δ
cpp	91.8% <100.0%> (-0.1%)	⬇️
python	95.9% <100.0%> (+<0.1%)	⬆️

Files Changed	Coverage Δ
include/cliffordsynthesis/Tableau.hpp	97.1% <ø> (ø)
src/mqt/qmap/load_calibration.py	100.0% <ø> (ø)
src/mqt/qmap/qiskit/backend.py	96.7% <ø> (ø)
src/heuristic/HeuristicMapper.cpp	91.2% <100.0%> (+<0.1%)	⬆️
src/mqt/qmap/__init__.py	64.7% <100.0%> (ø)
src/mqt/qmap/clifford_synthesis.py	98.7% <100.0%> (ø)
src/mqt/qmap/compile.py	96.2% <100.0%> (ø)
src/mqt/qmap/load_architecture.py	100.0% <100.0%> (ø)
src/mqt/qmap/subarchitectures.py	96.3% <100.0%> (ø)

... and 2 files with indirect coverage changes

[github-actions]

Cpp-Linter Report ✔️

No problems need attention.

Have any feedback or feature suggestions? Share it here.