base and pre-aggr table may not be consistent if the leader changes

**Bug Description**
- leaders of base and pre-aggr tables: is always consistent
- followers of base and pre-aggr tables: not consistent. they are synced from leaders separately.

If there is a change in the leadership, it may cause in-consistency:
- the offset of base is not consistent with the offset of pre-aggr
- the leaders of base and pre-aggr will not be in the same tablet. The leader of pre-aggr table will never be updated.

**Expected Behavior**

Potential solutions:
- leaders of base and pre-aggr tables are not necessary to be in the same tablet
- offset checking before updating the pre-aggr table:
- if base > pre-aggr + 1, there may be some data lost in pre-aggr. have to manually update the pre-aggr until the base latest
- if base <= pre-aggr + 1, there may be some data lost in base. have to remove the new data from pre-aggr

In order not to affect the online service, the pre-aggr update should be done asynchronously in the background.

**Relation Case**

**Steps to Reproduce**

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この issue は、分散データベースで leader が変更された際のベーステーブルと事前集計テーブル間の一貫性の問題について説明しています。OpenMLDB のソースコードにおける leader 選出とデータ同期のメカニズムを調査し、offset がどのように追跡・更新されるかに焦点を当ててください。テーブルレプリケーション、leader の遷移、バックグラウンド集計タスクを扱うモジュールを探し、現在のフローと不整合が発生する箇所を理解してください。

索引モデルが issue の本文から書いたものです。