reimplement leveldb in rust, with some new features.
- Search tired levels(L0 currently) in parellel;
- Gather writes from multiple threads at the same time into a single wal;
- Metrics and prometheus exporter;
- MVCC enabled.
- Support the async feature: provide the async versions of each interface;
- Support the Skiplist memtable;
- Support the dump and scan interfaces, and support manual compactions;
- More detailed metrics;
- Support the compare-and-set primitives;
- Support other features that are interesting in rocksdb.