Our self hosted runners are limited in quantity so we should preserve
them for workflows that actually require the additional resources
instead of tying them up on workflows that do not benefit from the
additional resources.
docker.io rate limits _should_ be addressed now. Switch back to
`debian-12` runners.
This is now a conditional within the `tests` workflow as we evaluate the
migration.
This reverts commit a99e2c62e6.
The self-hosted Github runners have been provisioned, and we can switch
to using them for evaluation.
To prefer Github-hosted runners, you can safely revert this commit.
See: t/123181.
