Notify reviewers how long unit tests took to run

**Is your feature request related to a problem? Please describe.**
Sometimes we might accidentally add unit tests that run too slowly (e.g. when they forget to mock the network or filesystem).

**Describe the solution you'd like**
It would be cool if our CI posted a comment about unit test run-time, so we could have our "code review" attention pulled to this sort of issue in the future. We are aiming for less than 10 seconds to run all unit tests. There are `pytest` plugins which will report that kind of thing.

**Describe alternatives you've considered**
Rather than burden reviewers with more things to look at, we could have PRs fail testing if unit tests take longer than 10 seconds to run.

Start by locating the repository's CI configuration and pytest setup; the issue does not name specific files or an existing reporting entry point. Review available pytest plugins and decide whether the intended outcome is a pull-request comment or a failure when all unit tests exceed 10 seconds. Done means the chosen CI behavior reports or enforces the runtime threshold.

Written by the indexing model from the issue text.