Consider not performing alias rewrite to the rest of the query when alias is a column name

[Jackie-Jiang]

E.g. SELECT SUM(a) AS a WHERE a > 10 will throw exception because it will be rewritten to SELECT SUM(a) AS a WHERE SUM(A) > 10

Also, seems alias is not allowed in WHERE clause in standard SQL: https://docs.oracle.com/cd/E17952_01/mysql-5.7-en/problems-with-alias.html.
Not sure if we should block alias rewrite in WHERE clause because it can cause backward incompatible.

[Jackie-Jiang]

cc @xiangfu0 for some input