feat: persistence with WAL

[ASjet]

Features

• Add trait raft::Persister for read/write WAL and snapshot.
• Implement append and replay WAL for raft committed log.
• Add interface for enabling raft persistence raft::RaftService::setup_persister()
• New crate persister implements raft::Persister trait.
  • persister::FilePersister use file for persistence.
• Enable persistence for radis.

Tests

• New raft/persist
• New persister/wal_not_exist
• New persister/rw_wal