Deprecate ConsistentHashFactory customization

There aren't any good reasons to use a ConsistentHashFactory implementation different than the default selected by StateTransferManagerImpl#pickConsistentHashFactory.

The configuration attribute made sense when the default was DefaultConsistentHashFactory, but SyncConsistentHashFactory is much better nowadays, and it's pretty much impossible to come up with an implementation that works in more than one cache mode with the current API.