Consider supporting PostgreSQL/openGauss search path feature

## Feature Request

### Is your feature request related to a problem?

No.

### Describe the feature you would like.

After issue #14004 is completed, ShardingSphere has supported SQL such as `CREATE SCHEMA`, `ALTER SCHEMA` and `DROP SCHEMA`, and allows users to specify schema modifiers when executing SQL, such as:

```sql
SELECT * FROM test.t_order;
```

This SQL will query the data of the t_order table from the test schema.

In order to improve the experience of using PostgreSQL/openGauss schema, we need to support the search_path parameter. Through the `SET SEARCH_PATH TO test, public;` statement, users can dynamically switch the schema without going through schema.t_order. For more detail about search_path, we can refer this doc——https://www.postgresql.org/docs/14/ddl-schemas.html#DDL-SCHEMAS-PATH.