Feature Request: Add Hostname to the `BackupManifest`

[rvrangel]

Feature Description

Sometimes filtering through backups outside of vitess can be complicated when all we have to identify the tablet that created a backup is the TabletAlias. So I would like to propose adding the Hostname as well there for completion and to make it easier to filter backups when not necessarily being used by Vitess APIs

Use Case(s)

We would be able to filter through backups created by a particular hostname, not just the TabletAlias, making it easier to find the right backup in some cases.