ISPN-4359 Provide an annotation driven way of declaring protobuf metadata
Implement purgeOnJoin

The joiner will still do the preload, but the entries will be removed from
the data container.

Also includes a fix for ISPN-3217 (entries not written to the cache store
on a backup owner with CACHE_MODE_LOCAL).

A hack was needed to avoid triggering ISPN-3443 (state transfer undoing the
remove operations).