truncate origin_sql in __all_plan_baseline_item to at most 10M

src/sql/spm/ob_plan_baseline_sql_service.h

@@ -111,6 +111,7 @@ public:
   int convert_sql_string(ObIAllocator &allocator,
                          const ObCollationType input_collation,
                          const ObString &input_str,
+                         bool truncate_str,
                          ObString &output_str);
 
   int update_plan_baselines_result(const uint64_t tenant_id,
@@ -134,6 +135,7 @@ public:
                                const ObBaselineKey& key,
                                const ObPlanBaselineItem& baseline_item);
 private:
+  static const int64_t max_sql_text_size = 10 * 1024 * 1024; // 10M
   const static char *EMPTY_STR;
   bool inited_;
   ObMySQLProxy* mysql_proxy_;