Refactor NeoStoreDataSource

Refactors NeoStoreDataSource into modules, and introduces Recovery,LogRotation, and LogPruning as separate processes.

The recovery process now works on its own channel to the underlying logs, so there is no longer any assumption that after recovery PhysicalLogicalLog can continue with the same channel. Instead it opens its own channel and moves to the end.

UpdateableSchemaState and its implementation didn't have anything to do with IAGD, so it was moved into NSDS.

Log pruning is now a separate process, that uses monitor callbacks to trigger when to run.
+1 I still think we should test for this since it's a property of the log implementation that we want, regardless of how it's implemented.