* Fix MultiVersionRepository BwC Tests
The HLRC doesn't like what its getting back from some older 6.x versions for the restore status
so I moved that request to the low level client.
Closes#50819
Follow up to #50692 that starts writing a `min_version` field to
the `RepositoryData` so that pre-7.6 ES versions can not read it
(and potentially corrupt it if they attempt to modify the repo contents)
after the repository moved to the new metadata format.
* Fix Snapshot Repository Corruption in Downgrade Scenarios (#50692)
This PR introduces test infrastructure for downgrading a cluster while interacting with a given repository.
It fixes the fact that repository metadata in the new format could be written while there's still older snapshots in the repository that require the old-format metadata to be restorable.
