[core] Add version-aware LocalKvDb range iterator

[JingsongLi]

Purpose

Add an efficient, version-aware prefix/range iteration primitive to LocalKvDb for ListState and SetState.

Changes

• Add lazy half-open range iteration over the memtable and overlapping SST files.
• Merge all sources in key order with newest-version-wins semantics.
• Suppress deleted keys through tombstones instead of exposing older values.
• Select overlapping non-L0 SST files with binary search.
• Hold a levels read snapshot while an iterator is open so concurrent compaction cannot delete its input files.
• Expose collecting and callback-based range scan conveniences.

Verification

• mvn -q -pl paimon-common -Pfast-build -DwildcardSuites=none '-Dtest=LocalKvDbTest#testRangeScanMergesMemTableAndLevels+testForEachInRangeAcrossMemTableAndSingleSst+testRangeIteratorDeduplicatesVersionsAcrossAllSources+testRangeIteratorCrossesSstBlocks,LocalKvDbAsyncCompactionTest#testAutomaticCompactionRunsInBackground+testRangeIteratorPreventsCompactionFromDeletingItsFiles' test
• mvn -q -pl paimon-common spotless:check -DskipTests
• mvn -q -pl paimon-common -DskipTests compile

[leaves12138]

There is one blocking mutation path missing the range-iterator guard. I reproduced the bulk-load operation blocking until the iterator is closed.

[leaves12138]

bulkLoad also mutates levels, but it does not call ensureNoRangeIterator(). rangeIterator() keeps the LsmLevels read lock until close, while bulkLoad() eventually calls levels.addFiles() and needs the write lock. With an iterator open on an empty DB, a concurrent bulk load blocks until close; invoking it on the iterator-owning thread deadlocks permanently because this lock cannot be upgraded. Please guard bulkLoad as well and add a regression test.