[SPARK-3708][SQL] Backticks aren't handled correctly is aliases

The below query gives error
sql("SELECT k FROM (SELECT \`key\` AS \`k\` FROM src) a")
It gives error because the aliases are not cleaned so it could not be resolved in further processing.

Author: ravipesala <ravindra.pesala@huawei.com>

Closes #2594 from ravipesala/SPARK-3708 and squashes the following commits:

d55db54 [ravipesala] Fixed SPARK-3708 (Backticks aren't handled correctly is aliases)