[SPARK-13535][SQL] Fix Analysis Exceptions when Using Backticks in Transform Clause

#### What changes were proposed in this pull request?
```SQL
FROM
(FROM test SELECT TRANSFORM(key, value) USING 'cat' AS (`thing1` int, thing2 string)) t
SELECT thing1 + 1
```
This query returns an analysis error, like:
```
Failed to analyze query: org.apache.spark.sql.AnalysisException: cannot resolve '`thing1`' given input columns: [`thing1`, thing2]; line 3 pos 7
'Project [unresolvedalias(('thing1 + 1), None)]
+- SubqueryAlias t
   +- ScriptTransformation [key#2,value#3], cat, [`thing1`#6,thing2#7], HiveScriptIOSchema(List(),List(),Some(org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe),Some(org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe),List((field.delim,	)),List((field.delim,	)),Some(org.apache.hadoop.hive.ql.exec.TextRecordReader),Some(org.apache.hadoop.hive.ql.exec.TextRecordWriter),false)
      +- SubqueryAlias test
         +- Project [_1#0 AS key#2,_2#1 AS value#3]
            +- LocalRelation [_1#0,_2#1], [[1,1],[2,2],[3,3],[4,4],[5,5]]
```

The backpacks of \`thing1\` should be cleaned before entering Parser/Analyzer. This PR fixes this issue.

#### How was this patch tested?

Added a test case and modified an existing test case

Author: gatorsmile <gatorsmile@gmail.com>

Closes #11415 from gatorsmile/scriptTransform.