Draft: Fail pytest on deprecation/future warnings (QAE-993)

Explanation of changes

• Ensure that pytest does not pass when using deprecated code
• Fix usage of deprecated code.

Motivation of changes

If we rely on deprecated functionality, then we should not deprecate it.

Follow-up to !553 (merged)

---

Merge checklist

See also merge request guidelines

• Merge request has been reviewed (in-depth by a knowledgeable contributor), and is approved by a project maintainer.
• New code is covered by unit tests (or N/A).
• New code is documented and docstrings use numpydoc format (or N/A).
• New functionality: considered making private instead of extending public API (or N/A).
• Public API changed: added @deprecated (or N/A).
• Tested on hardware (or N/A).
• CHANGELOG.md and AUTHORS.md have been updated (or N/A).
• Windows tests in CI pipeline pass (manually triggered by maintainers before merging).

---

For reference, the issues workflow is described in the contribution guidelines.