ARROW-11771: [Developer][Archery] Move benchmark tests (so CI runs them)

[dianaclarke]

I recently added additional tests to:

https://github.com/apache/arrow/blob/master/dev/archery/tests/test_benchmarks.py

But just noticed that they aren't actually being executed by CI (because they aren't in the expected location):

      - name: Archery Unittests
        working-directory: dev/archery
        run: pytest -v archery

Here you can see them running now.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11771

[kou]

+1