Subscription: Fix DATE serialization for consensus dataset

[Caideyipi]

Description

Problem

For table-model topics with format=dataset and mode=consensus, DATE columns in WAL insert nodes are represented as int[]. ConsensusLogToTabletConverter reused those arrays in a TsFile Tablet, whose DATE serialization requires LocalDate[]. The resulting array type mismatch prevented subscription events from being generated, so pull consumers repeatedly received no messages.

Reproduction: https://gitlab-eco.timecho.com/test/pipe-client/-/commit/1dcc9ccbbb2e6ee1ab8e8c95231dd05e314d08f4

Fix

• Convert DATE columns from the WAL int[] representation to the Tablet LocalDate[] representation.
• Preserve null semantics by skipping bitmap-marked positions during conversion.
• Apply the same representation boundary to row-based consensus conversions while retaining already-normalized LocalDate values.

Tests

• Added a regression test using the reported 2026-01-31 DATE value.
• The test serializes and deserializes the converted Tablet to verify the dataset payload path.
• ConsensusLogToTabletConverterTest: 13 tests passed.
• Reactor build for iotdb-core/datanode and required upstream modules passed.

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This PR has:

• been self-reviewed.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage.

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Key changed/added classes (or packages if there are too many classes) in this PR

• ConsensusLogToTabletConverter
• ConsensusLogToTabletConverterTest