This commit implements the replication transport layer as part of Phase 2 of the replication plan.
Key components include:
- Add protocol buffer definitions for replication services
- Implement WALReplicator extension for processor management
- Create replication service server implementation
- Add replication client and server transport implementations
- Implement storage snapshot interface for bootstrap operations
- Standardize package naming across replication components
- Add replication-specific interfaces to pkg/transport
- Create ReplicationClient and ReplicationServer interfaces
- Add replication message types for WAL entries and bootstrap
- Create Protobuf schema for replication in proto/kevo/replication.proto
- Update transport registry to support replication components
