PageMemory Persistent Store porting and refactoring

Ignite 2.x storage based on PageMemory shows good performance on read-intensive workloads and can be used both in in-memory and persistent scenarios.

So it can be employed in Ignite 3.0 for use-cases where RocksDB is less effective.

At the same time Ignite 3.0 already has Raft-based replication protocol which can provide logging service for PageMemory-based storage.
This allows implementing more efficient and reliable algorithms of logging and checkpointing.

A more detailed overview of these algorithms is available in this document.