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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Das Issue beschreibt ein Konsistenzproblem zwischen Basis- und Pre-Aggregationstabellen während Leader-Wechseln in einer verteilten Datenbank. Untersuche den Quellcode von OpenMLDB auf die Mechanismen zur Leader-Wahl und Datensynchronisierung und konzentriere dich darauf, wie Offsets erfasst und aktualisiert werden. Suche nach Modulen, die die Tabellenreplikation, Leadership-Übergänge und Hintergrund-Aggregationsaufgaben behandeln, um den aktuellen Ablauf und die Ursache der Inkonsistenz zu verstehen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.