[SPARK-8658] [SQL] [FOLLOW-UP] AttributeReference's equals method compares all the members

[gatorsmile]

Based on the comment of @cloud-fan in #9216, update the AttributeReference's hashCode function by including the hashCode of the other attributes including name, nullable and qualifiers.

Here, I am not 100% sure if we should include name in the hashCode calculation, since the original hashCode calculation does not include it.

@marmbrus @cloud-fan Please review if the changes are good.

[SparkQA]

Test build #46069 has finished for PR 9761 at commit eb63f09.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

@nongli I saw you have a related discussion with @chenghao-intel . The failed test case was introduced in your PR #9480. I am not sure the root reason why we intentionally exclude name from hashCode, but the original equals includes name. It breaks a general principle of hashCode function design:

An object’s hashCode method must take the same fields into account as its equals method. 

Based on my understanding, in a case-insensitive HiveContext, we still should detect their differences when the case of name is different but the exprId values are the same

[nongli]

This change looks good to me. The failing test is not valid anymore and should be changed to verify that the hash codes are not equal.

[gatorsmile]

Ok. I will also add three more lines for covering the new hashCode and equals functions.

[SparkQA]

Test build #46095 has finished for PR 9761 at commit b2e354a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[marmbrus]

Thanks! Merging to master and 1.6.