[SPARK-7235] [SQL] Refactor the grouping sets

[chenghao-intel]

The logical plan Expand takes the output as constructor argument, which break the references chain. We need to refactor the code, as well as the column pruning.

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Merged build triggered.

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Merged build started.

[SparkQA]

Test build #31283 has started for PR 5780 at commit c4395b4.

[chenghao-intel]

cc @viirya @marmbrus

[SparkQA]

Test build #31283 has finished for PR 5780 at commit c4395b4.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.

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Merged build finished. Test FAILed.

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Test FAILed.
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Test FAILed.

[chenghao-intel]

The failure depends on #5798

[liancheng]

Hey @chenghao-intel, per our offline discussion, we can fix the case sensitivity issue in a surgical way within this PR (by comparing attribute names in a case insensitivity way when necessary), so that #5798 doesn't bock this one.

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Merged build triggered.

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Merged build started.

[SparkQA]

Test build #35549 has started for PR 5780 at commit 76e4aa4.

[SparkQA]

Test build #35549 has finished for PR 5780 at commit 76e4aa4.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class BroadcastHint(child: LogicalPlan) extends UnaryNode

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Merged build finished. Test PASSed.

[marmbrus]

Thanks, this looks a lot cleaner. Merging to master.