💥 Move matrix generation to calling workflow

[denialhaag]

Description

This PR simplifies some reusable workflows by moving the matrix generation to the calling workflows.

Checklist:

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

[burgholzer]

This is great already. I just have one comment on the Python testing workflow, which might need some further changes.

[burgholzer]

This looks really good. I like where this is going. I only have two small little comments that should be fairly easy to address.
Feel free to also directly prepare another release as part of this PR. Should probably be another minor one.

[burgholzer]

Awesome, let's go 🚀