issue: #41544
- Implement in-memory shard manager to maintain the shard state at write
ahead.
- Remove all rpc and meta operation at write ahead, make the segment
assignment logic only use wal and memory.
- Refactor global stats management, add node-level flush policy.
- Fix the recovery storage inconsistency bug when graceful close.
Signed-off-by: chyezh <chyezh@outlook.com>