Propagate Conf.default_bucket_num to CREATE TABLE AS SELECT. (#14160)

Previously, Conf.default_bucket_num only applies to CREATE TABLE. CREATE TABLE AS SELECT used a hard-coded default bucket num of 10.

This PR propagates Conf.default_bucket_num to CREATE TABLE AS SELECT.

(cherry picked from commit 1ad9ab3)

fe/fe-core/src/main/java/com/starrocks/sql/analyzer/CTASAnalyzer.java

@@ -13,6 +13,7 @@
 import com.starrocks.catalog.OlapTable;
 import com.starrocks.catalog.Table;
 import com.starrocks.catalog.Type;
+import com.starrocks.common.Config;
 import com.starrocks.common.Pair;
 import com.starrocks.qe.ConnectContext;
 import com.starrocks.server.GlobalStateMgr;
@@ -141,7 +142,7 @@ public static void analyze(CreateTableAsSelectStmt createTableAsSelectStmt, Conn
                 }
             }
 
-            int defaultBucket = 10;
+            int defaultBucket = Config.default_bucket_num;
             DistributionDesc distributionDesc =
                     new HashDistributionDesc(defaultBucket, Lists.newArrayList(defaultColumnName));
             createTableStmt.setDistributionDesc(distributionDesc);