[AMORO-4163][ams] Fix Version-N-already-exists race in newTableOperations for legacy mixed-iceberg (#4185)

When AMS saves a new legacy mixed-iceberg table to the database, a background
table-explorer thread can concurrently pick up the same table and call
newTableOperations(), which now commits the mixed-format properties to the
Iceberg metadata (introduced by the AMORO-4163 fix).  If the background thread
wins the race and writes v2.metadata.json before the onTableCreated() path
attempts the same commit, HadoopTableOperations throws CommitFailedException:
"Version 2 already exists", aborting the createTableMeta RPC.

Fix: catch CommitFailedException in the commit block, refresh to obtain the
latest on-disk metadata, and proceed if a concurrent writer already committed
the correct properties.  Re-throw only when the properties still differ after
refresh, indicating a genuine commit conflict.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: lintingbin

amoro-ams/src/main/java/org/apache/amoro/server/table/internal/InternalMixedIcebergHandler.java

@@ -32,6 +32,7 @@
 import org.apache.hadoop.fs.Path;
 import org.apache.iceberg.TableOperations;
 import org.apache.iceberg.catalog.TableIdentifier;
+import org.apache.iceberg.exceptions.CommitFailedException;
 
 import java.util.Map;
 
@@ -81,7 +82,18 @@ private TableOperations newTableOperations(boolean changeStore) {
       org.apache.iceberg.TableMetadata legacyCurrent = legacyTableMetadata(current, changeStore);
       if (!current.equals(legacyCurrent)) {
         // add rest based mixed-format table properties
-        ops.commit(current, legacyCurrent);
+        try {
+          ops.commit(current, legacyCurrent);
+        } catch (CommitFailedException e) {
+          // A concurrent caller (e.g. background table-explorer racing with onTableCreated) may
+          // have already committed the same property update. Refresh to get the latest metadata;
+          // if properties are now up-to-date, proceed normally. Otherwise re-throw.
+          current = ops.refresh();
+          legacyCurrent = legacyTableMetadata(current, changeStore);
+          if (!current.equals(legacyCurrent)) {
+            throw e;
+          }
+        }
       }
       return ops;
     }