[SPARK-19471][SQL] AggregationIterator does not initialize the generated...

[SPARK-19471][SQL] AggregationIterator does not initialize the generated result projection before using it

## What changes were proposed in this pull request?

Recently, we have also encountered such NPE issues in our production environment as described in:
https://issues.apache.org/jira/browse/SPARK-19471

This issue can be reproduced by the following examples:
` val df = spark.createDataFrame(Seq(("1", 1), ("1", 2), ("2", 3), ("2", 4))).toDF("x", "y")

//HashAggregate, SQLConf.WHOLESTAGE_CODEGEN_ENABLED.key=false
df.groupBy("x").agg(rand(),sum("y")).show()

//ObjectHashAggregate, SQLConf.WHOLESTAGE_CODEGEN_ENABLED.key=false
df.groupBy("x").agg(rand(),collect_list("y")).show()

//SortAggregate, SQLConf.WHOLESTAGE_CODEGEN_ENABLED.key=false &&SQLConf.USE_OBJECT_HASH_AGG.key=false
df.groupBy("x").agg(rand(),collect_list("y")).show()`
`

This PR is based on PR-16820(https://github.com/apache/spark/pull/16820) with test cases for all aggregation paths. We want to push it forward.

> When AggregationIterator generates result projection, it does not call the initialize method of the Projection class. This will cause a runtime NullPointerException when the projection involves nondeterministic expressions.

## How was this patch tested?

unit test
verified in production environment

Author: donnyzone <wellfengzhu@gmail.com>

Closes #18920 from DonnyZone/Branch-spark-19471.