[core][flink] Detect overwrite conflicts for index commits

[leaves12138]

Purpose

Prevent stale row-id-sensitive global index commits after later OVERWRITE snapshots change row-id/index safety.

Changes

• Add overwrite conflict checking via commit.overwrite-conflict.last-safe-snapshot.
• Mark row-id reassignment snapshots with the transient overwrite-barrier snapshot property.
• Abort index commits when a later overwrite barrier snapshot exists, or when a later ordinary overwrite snapshot touches the target partitions.
• Wire Flink btree/generic global index commits to pass the scan snapshot through dynamic commit options.
• Keep the transient overwrite barrier property out of normal manifest rewrite and compact snapshots.
• Add tests for overwrite barrier detection, overlapped overwrite detection, barrier property cleanup, and row-id reassignment metadata.

Validation

• git diff --check
• mvn -pl paimon-flink/paimon-flink-common -am -Pfast-build -DskipTests compile
• mvn -pl paimon-spark/paimon-spark-common -am -Pfast-build -DskipTests compile
• mvn -pl paimon-core -am -Pfast-build -DfailIfNoTests=false -Dtest=ConflictDetectionTest#testDetectsOverwriteBarrierSnapshotConflict+testIgnoresOverwriteBarrierPropertyOnNonOverwriteSnapshot+testDetectsOverlappedOverwriteSnapshotForIndexCommit+testIgnoresNonOverlappedOverwriteSnapshotForIndexCommit test was attempted locally, but this environment fails during paimon-core test compilation because the existing shaded Parquet test dependency is unavailable (org.apache.paimon.shade.org.apache.parquet.hadoop).
• GitHub Actions currently fail during checkout with remote: Your account is suspended / HTTP 403, before project build/test execution.

[JingsongLi]

Can we just reuse setRowIdCheckFromSnapshot?

[leaves12138]

Thanks for the suggestion. I think these two snapshot markers should stay separate because they guard different invariants. rowIdCheckFromSnapshot is used by row-id range / column-level conflict checks, while this one is driven by commit.row-id-reassign.last-safe-snapshot and scans later OVERWRITE snapshots for row-id reassign or overlapped partition overwrite conflicts during index build/compact commits. Reusing the existing field would couple two independent checks and make the COMPACT/index path harder to reason about.

[jerry-024]

Overall LGTM. Three minor optimization suggestions below — none are blockers.

[jerry-024]

nit: Can be simplified to:

Long rowIdReassignCheckFromSnapshot = indexBuilder.scanSnapshotId().orElse(null);

Optional.orElse(null) is idiomatic and avoids the double method call.

[jerry-024]

nit: This method is identical to BTreeIndexTopoBuilder.withRowIdReassignCheck. Consider extracting to a shared utility to avoid drift if the option key or logic changes later. Not blocking — the method is small.

[jerry-024]

suggestion: Consider adding a test that verifies compactManifestOnce also strips ROW_ID_REASSIGN_PROPERTY. Current tests cover replaceManifestList but not the compact path.