Replace minio with garage

Synopsis
buildbot.mariadb.org requires an S3 storage service for extending tests coverage
by running the server's MTR s3 suite.

Rationale
Since minio discontinued their community support:
https://github.com/minio/minio/issues/21647

we need to move away to an open-source alternative
that will replace minio.mariadb.org so we stay up to date with any
further development of the S3 API and security updates.

faust proposed garage https://garagehq.deuxfleurs.fr/.

Changes:

• on the infra side, a garage instance will be deployed on the mariadb.org domain
• on buildbot side, the configuration should be updated to use this instance