The SQL of `insert set` can not run well when sharding
## Bug Report

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### Which version of ShardingSphere did you use?
4.0.0-RC1
### Which project did you use? Sharding-JDBC or Sharding-Proxy?
Sharding-JDBC
### Expected behavior
`insert into t_order set order_id =1, user_id =1; ` can run well.
### Actual behavior
throw exception:
> ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'org.apache.shardingsphere.core.rewrite.placeholder.InsertSetPlaceholder@2f60192a'

### Reason analyze (If you can)
SQLBuilder does not handle `InsertSetPlaceholder`.
### Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

### Example codes for reproduce this issue (such as a github link).

diff --git a/sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/SQLBuilder.java b/sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/SQLBuilder.java
index 468b450962a..221a2cbf223 100644
--- a/sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/SQLBuilder.java
+++ b/sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/SQLBuilder.java
@@ -114,6 +114,8 @@ public final class SQLBuilder {
                 appendIndexPlaceholder((IndexPlaceholder) each, actualTableName, result);
             } else if (each instanceof InsertValuesPlaceholder) {
                 appendInsertValuesPlaceholder(tableUnit, (InsertValuesPlaceholder) each, insertParameters, result);
+            } else if (each instanceof InsertSetPlaceholder) {
+                appendInsertSetPlaceholder(tableUnit, (InsertSetPlaceholder) each, insertParameters, result);
             } else {
                 result.append(each);
             }
['sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/SQLBuilder.java']