Update OSX persistent ccache to leverage new storage.

MacStadium is deprecating the "shared VM storage" that comes with the Orka Cluster, and, as we have seen, has also caused us some issues in the past with NFS breaking.

I just got off a call with them and they've agreed to offer us another singular bare metal mac that we can use as a persistent node alongside our existing cluster where we can put our shared ccache.

There are a couple ways forward on this machine:

1. expose the drive as a network file share to the orka nodes that mount it as they come up so they access the cache via the filesystem
2. Install Redis/Valkey on the new node and use ccache's ability to leverage that.

My preference is 2, as Im suspicious of network filesystems, and I believe that a Redis/Valkey cache will be performant enough to satisfy our requirements.

Start by reviewing the current OSX persistent ccache setup and how Orka nodes mount the existing shared storage. Compare the proposed Redis/Valkey cache on the new bare-metal Mac with exposing its drive as a network share; done means the Orka nodes use persistent ccache without relying on the deprecated shared VM storage.