feat(ci): set concurrency for test workflow

[l-lumin]

This update ensures that workflows always run on the latest commit

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/control-the-concurrency-of-workflows-and-jobs

note: did not add concurrency to the pre-commit workflow as it currently only uses Black. Since Hatch has Ruff built-in, we can merge the pre-commit workflow into the test workflow later for better efficiency

Static analysis performed by the fmt command is (by default) backed entirely by Ruff. https://hatch.pypa.io/latest/config/internal/static-analysis/