Add support for Python 3.12

[ghisvail]

When running the medkit test suite for Python 3.12, the following error is triggered with importing iamsystem:

TypeError: type ‘typing.TypeVar’ is not an acceptable base type

This is a bug in typing_extensions, which is fixed in a newer release (starting from version 4.7).

This PR updates the project metadata and dependencies to provide support and run tests on Python 3.12.

• Bump minimum version of typing_extensions to the one with official support for Python 3.12
• Update trove classifiers in project metadata
• Enable tests for Python 3.12 in CI
• Use setup-python@v5 caching capabilities

[ghisvail]

Is there any specific reason to have such a strict requirement for typing_extensions?

typing_extensions~=4.4.0 means downstream projects using iamsystem are stuck with your version (4.4.x) and cannot benefit from further improvements and bug fixes to the package, such as the fixes introduced for Python 3.12 since version 4.7.

Although my PR should work as is, such constraints are officially discouraged, especially for libraries. Maybe we could revisit whether such constraint (still) is necessary?

[scossin]

Thanks for the changes