[core] Optimize overwrite retry with incremental scan

[leaves12138]

Purpose

Overwrite commits rebuild the target partition file set before every atomic commit retry. For large partitions this repeatedly performs a full manifest scan after commit conflicts, which can make retries very expensive.

Changes

• Add a stateful overwrite CommitChangesProvider in CommitScanner.
• Keep the first overwrite attempt behavior as a full target scan.
• On later retries, update the cached target file set from snapshot DELTA manifests between the previous checked snapshot and the latest snapshot.
• Use the provider from the common overwrite path, so both normal insert overwrite and drop/truncate partition paths are covered.
• Keep index overwrite changes based on the latest index manifest on each retry.
• Add a retry test for partial-partition insert overwrite with a concurrent commit between attempts.

Tests

• mvn -pl paimon-api,paimon-test-utils,paimon-common,paimon-codegen,paimon-codegen-loader,paimon-arrow,paimon-format -DskipTests install
• mvn -pl paimon-core -DskipITs -Dtest=FileStoreCommitTest#testOverwriteRetryUpdatesCurrentFilesWithDelta test
• mvn -pl paimon-core -DskipITs -Dtest=FileStoreCommitTest#testOverwritePartialCommit+testDropPartitions+testIndexFiles+testDropStatsForOverwrite+testOverwriteRetryUpdatesCurrentFilesWithDelta test
• mvn -pl paimon-core -DskipITs -Dtest=FileStoreCommitTest test