`long window` supports base table with existing data

**Describe the feature you'd like**

If data is loaded into the table before the deployment with long window option,
we should build the pre-aggregation table on the fly (asynchronous).

**Additional context**

Add any other context or screenshots about the feature request here.

The issue mentions 'long window' and building a pre-aggregation table asynchronously for existing data. Research the OpenMLDB codebase for long window handling and pre-aggregation logic. Look for existing table deployment and data loading paths. Determine how to trigger an asynchronous build process and integrate it with the existing data flow.

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