Update XCache container docs to use prescribed locations
In , we changed the XCache containers to use prescriptive namespace, data, and metadata locations. These locations support two different styles of volume mounts:
Multiple host disks (preferred): mount SSDs to /xcache/meta*, and HDDs to /xcache/namespace and /xcache/data*
Single host disk: mount disk to /xcache
It'd be nice to have a section about transitioning a single disk setup to a multi-disk setup but that can be separated out into another ticket if need be.
Marking this RFT since we’re waiting to get the stash-cache and stash-origin containers marked as stable, which is waiting on to validate this PR: