[littlegrasscao]

Summary

• convert jsonPredicateHints to a Kernel predicate for ScanBuilder.withFilter, so Kernel prunes partitions and skips files by min/max stats
• hints are best effort, as in the Delta Sharing server: oversized, too deep, malformed, or unsupported hints return every file instead of an error
• the deprecated SQL predicateHints are logged at debug and never filter
• apply limitHint only when no predicate hint is present, stopping once the returned files cover the limit (stats.numRecords minus deletion vector cardinality)
• read scan files with stats, so file actions include stats
• clients still filter rows and apply the limit, so returning extra files is always correct

Testing

• mvn clean install: 220 tests passed
• JsonPredicateHintsTest: every op and value type, and/or/not/isNull, bool leaves, the depth limit, and hints that are skipped
• DeltaTableQueryReaderTest: partition pruning, stats-based skipping, an unsupported hint, and the limitHint cutoff on a local Delta log, with stub signing instead of Mockito
• ProtocolTablePushdownIntegrationTest: limits and filters on the S3, Azure, and GCS test tables; each case is skipped without credentials

Stacked on #110.