Add support for Python 3.12, drop support for Python 3.8

[wilfried-huss]

Summary

Add support for Python 3.12.

Because of dependency conflicts, remove support for Python 3.8. This major version is not actively supported since May 2021 and security support will end in October 2024.

Details and comments

• update workflows to use Python 3.11 for non version-critical tasks;
• update tooling to use Python 3.9 as target version. This triggers using standard containers as type annotations instead of dedicated imports from the typing module;
• upgrade all dependencies. Qiskit dependencies are constrained further, to ensure Python 3.12 support:
  • Qiksit >= 0.45.2
  • Qistkit-Aer >= 0.13.2.

[airwoodix]

symengine 0.11 was released, with Python 3.12 wheels.
We can continue on this patch as soon as Qiskit/qiskit#11262 is released.

[airwoodix]

Python 3.8 cannot be supported at the same time as Python 3.12, because numpy dropped support for Python 3.8 in 1.25.0. Numpy >=1.26.0 is required for Python 3.12 support (see 1680dec).

qiskit-aer doesn't ship Python 3.12 wheels yet. Building on demand fails. This may be fixed by Qiskit/qiskit-aer#1947.

[mtreinish]

Aer has support for Python 3.12 now with Qiskit/qiskit-aer#2022 which was recently published in 0.13.2.

[airwoodix]

@mtreinish thanks for the hint and the work on Python 3.12 support for Qiskit-Aer! It's great to have Python 3.12 support for all the dependencies in this package now.

@wilfried-huss I think this PR is ready now. Since you're the original author, I can only ask you for a review like this :)