[HOTFIX] [SQL] Fix the failed test cases in GeneratorFunctionSuite

[gatorsmile]

What changes were proposed in this pull request?

Multiple tests failed. Revert the changes on supportCodegen of GenerateExec. For example,

• https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/75194/testReport/

How was this patch tested?

N/A

[gatorsmile]

cc @rxin

[gatorsmile]

It sounds like the codegen version has a bug. It did not respect the following logics:

@param outer when true, each input row will be output at least once, even if the output of the
             given `generator` is empty. `outer` has no effect when `join` is false.

[SparkQA]

Test build #75203 has finished for PR 17425 at commit f9d9082.

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

[SparkQA]

Test build #75204 has finished for PR 17425 at commit 48b73db.

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

[SparkQA]

Test build #75206 has finished for PR 17425 at commit 206370d.

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

[gatorsmile]

Merging to master!

[viirya]

@gatorsmile I'm exploring Generate related code. I'm curious why you don't revert the supportCodegen back in the end?

[kiszk]

@gatorsmile I have the same question. Which operation in Generator is bad? All of them, or only one?