Support batch read for PK tables based on SST files

[loserwang1024]

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Description

The parent issue proposes an SST-file-based batch read approach for PK tables. This issue implements the core KvSnapshotAndLogBatchScanner, following the pattern of LakeSnapshotAndLogSplitScanner but replacing the lakehouse snapshot data source with KV snapshot SST files.

Willingness to contribute

• I'm willing to submit a PR!