Optimize: CI Pipeline

[JakobEliasWagner]

Optimize: CI Pipeline

Description

This pr introduces caching into the setup of dependencies of the runners. This significantly speeds up testing. Reduces CI pipeline runtime by up to 5 minutes.

Which issue does this PR tackle?

• CI pipeline very slow.
• This disrupts the workflow in pull requests.

How does it solve the problem?

• Introduces cached virtual environments to the workflows.
• Only when dependencies change do these environments need to be changed.
• Cached venvs discriminate between os, python version, and the current dependencies.
• Splits up testing into regular tests in run_tests and notebook tests run_tests_notebooks (total of 13 test ci jobs) .

How are the changes tested?

• Pipelines work as they did before.
• Empty commit to ensure the cached venvs are used.

Checklist for Contributors

• [x] Scope: This PR tackles exactly one problem.
• [x] Conventions: The branch follows the feature/title-slug convention.
• [x] Conventions: The PR title follows the Bugfix: Title convention.
• [x] Coding style: The code passes all pre-commit hooks.
• [x] Documentation: All changes are well-documented.
• [x] Tests: New features are tested and all tests pass successfully.
• [x] Changelog: Updated CHANGELOG.md for new features or breaking changes.
• [x] Review: A suitable reviewer has been assigned.

Checklist for Reviewers:

• [x] The PR solves the issue it claims to solve and only this one.
• [x] Changes are tested sufficiently and all tests pass.
• [x] Documentation is complete and well-written.
• [x] Changelog has been updated, if necessary.

[JakobEliasWagner]

I will not be adding cached dependencies to the code quality workflow as it is very fast already and does not need this.

[JakobEliasWagner]

@samuelburbulla currently the pr is waiting for 2 expected checks run_tests_macos and run_tests_ubuntu. I combined these tests into a single matrix strategy called run_tests. Additionally, I split up the test into run_tests and run_tests_notebooks to be able to run them in parallel (as dependencies are cached and do not need to be built every time. I think that the main branch is currently protected with the "Require status checks to pass before merging" option with both of these (deprecated) names listed. Would you please have a look at that and if true adjust these names. Thank you :)