group by with keyword alias miss back quote when rewriting

[tuohai666]

Bug Report

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Which version of ShardingSphere did you use?

4.0.0-RC2-SNAPSHOT

Which project did you use? Sharding-JDBC or Sharding-Proxy?

Sharding-JDBC and Sharding-Proxy

Expected behavior

logical SQL:
SELECT SUM(order_id) AS orders_sum, user_id as key FROM t_order GROUP BY key
actual SQL:
SELECT SUM(order_id) AS orders_sum, user_id as key FROM t_order GROUP BY key ORDER BY 'key' ASC

Actual behavior

SELECT SUM(order_id) AS orders_sum, user_id as key FROM t_order GROUP BY key ORDER BY key ASC

Reason analyze (If you can)

miss back quote when rewriting

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).

[tuohai666]

Fixed via #2817