WAL Mode in LiteFS

LiteFS is a distributed file system that replicates SQLite databases across multiple servers. It now supports all journaling modes, including the write-ahead log (WAL) mode, which improves concurrency and write performance. LiteFS keeps distributed copies of databases in sync by tracking changes as "change sets" and communicating them between nodes. The new litefs import command simplifies converting an existing application to use LiteFS. Additionally, the reworked checksumming method ensures database consistency across all nodes. Improved debugging with the trace log helps identify issues in LiteFS. Upcoming work includes supporting write forwarding and adding LZ4 compression for better performance.