feat: support batch cas
Summary
- Add new DML op: Batch, which allows using multiple dml operations in one CAS request
- If request has too many dml operations, the batch will be splitted into multiple batches, so that each batch can be stored in raft log
- Close #406 (closed)
- Target branch: master
- Docs follow-up: not necessary / new issue
Edited by Arseniy Volynets