Add support for accessing data through hpc-cache

There are situations where the same data can be accessed via different paths.

A common example on azure is data being read and written sequentially from blob storage, but a need for random access from roxie to be via hpc-cache.

A second example is where blob storage is normally mounted via nfs, but we would prefer to use direct access to the blob api (for copying or other examples).

The proposal is to add a set of access aliases within a data plane. This would allow the pvcs and mount points to be overridden for the different ways of accessing the data.

The details of the implementation will be added as a comment.

millti01 FYI, aiming to implement for 8.6.16