RHEL7 and Centos7 are EOL and because of that there no longer is a free maintained mirrorlist for their packages. Our package testing relies on centos7 containers currently since we're still committed to supporting RHEL7 until 2026.

(For context, our package testing is testing that the RPM/DEB images that we publish can be installed on each supported platform without error)

RHEL7 still is supported by Red Hat with an extended life support subscription. Use the rhel93 hosts that t.ward@mongodb.com setup with subscription keys to mount the keys into a ubi7 container for package testing. This gives us access to Red Hat's mirrorlist to get up-to-date packages.

Addresses https://jira.mongodb.org/browse/BF-34019